Plenary Oral Presentations - Macquarie University Hospital

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaBE-28Gamma Knife Radiosurgery for the Management of GlomusTumors: A Multicenter Study1Jason Sheehan, 9 Shota Tanaka, 2 Michael J Link, 3 Douglas Kondziolka, 4 David Mathieu,5Christopher Duma, 6 A. Byron Young, 7 Anthony M Kaufmann, 8 Heyoung McBride,1Zhiyuan Xu, 3 L. Dade Lunsford1University of Virginia, 2 Mayo Clinic, 3 University of Pittsburg, 4 University of Sherbrooke,5Hoag Memorial Hospital, 6 University of Kentucky, 7 University of Manitoba,8Barrow Neurological Institute and Arizona Oncology Services Foundation,9Massachusetts General Hospital,Objective: Glomus tumors are rare skull base neoplasms that frequently involve critical cerebrovascularstructures and lower cranial nerves. Complete resection is often difficult and may increase cranialnerve deficits. Stereotactic radiosurgery has gained an increasing role in the management of patientswith glomus tumors. This study examines the outcomes after radiosurgery in a large, multicenterpatient population.Methods: Under the auspices of the North American Gamma Knife Consortium (NAGKC), eightGamma Knife radiosurgery (GKRS) centers that treat glomus tumors retrospectively combined theiroutcome data. One hundred and thirty four patients were included in the study. Prior resection wasperformed in 51 patients and prior fractionated external beam radiotherapy was performed in sixpatients. Median age at the time of radiosurgery was 59 years. Forty percent of patients had pulsatiletinnitus at the time of radiosurgery. Patients received a median dose of 15 Gy to the tumor margin.The median follow-up was 50.5 months (range 5 to 220 months).Results: Overall tumor control was achieved in 93% of patients at last follow up; actuarial tumorcontrol was 88% at 5 years post-radiosurgery. The absence of trigeminal nerve dysfunction at the timeof radiosurgery (p=0.001), and higher number of isocenters (p=0.005) were statistically associatedwith progression free tumor survival. Those demonstrating new or progressive cranial nerve deficitswere also likely to demonstrate tumor progression (p=0.002). Pulsatile tinnitus improved in 49% ofpatients who demonstrated it at presentation. New or progressive cranial nerve deficits were noted in15% of patients; improvement in pre-existing cranial nerve deficits was observed in 11% of patients.No patient died as a result of tumor progression.Conclusions: Gamma Knife radiosurgery was a well tolerated management strategy that provided ahigh rate of long term glomus tumor control. Symptomatic tinnitus improved in almost one half of thepatients. Overall neurological status and cranial nerve function were preserved or improved in the vastmajority of patients after radiosurgery.2

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaBE-30Gamma Knife Radiosurgery of Skull Base Meningiomas:Analysis of Long-Term ResultsJason SheehanDepartment of Neurological Surgery, University of VirginiaObjective: Skull base meningiomas are challenging tumors owing in part to their close proximity toimportant neurovascular structures. Complete microsurgical resection can be associated with significantmorbidity, and recurrence rates are not inconsequential. In this study, we evaluate the outcomesof skull base meningiomas treated with Gamma Knife radiosurgery (GKRS) both as an adjunct tomicrosurgery and as a primary treatment modality.Methods: We performed a retrospective review of a prospectively compiled database detailing theoutcomes of 290 patients with skull base meningiomas treated at the University of Virginia from1989 to 2006. All patients had a minimum follow-up of 24 months. There were 60 males and 230females with a median age of 55 years (range 19-85). One hundred sixty one patients were treatedwith upfront radiosurgery, and 129 patients were treated following surgical resection. Factors predictiveof new neurological deficit following GKRS were assessed via univariate and multivariateanalysis, and Kaplan-Meier analysis and Cox multivariate regression analysis was used to assessfactors predictive of tumor progression.Results: Patients had meningiomas centered over the tentorium (35; 12%), cerebellopontine angle(43; 15%), petroclival region (28; 10%), petrous region (6; 2%), clivus (40; 14%), and parasellar(138; 48%). The median follow-up was 6.3 years (range 2-18 years). The mean pre-radiosurgerytumor volume was 6.6 cc.251 patients (87%) displayed no change or decrease in tumor volume, and 39 (13%) displayed anincrease in volume. Kaplan Meier analysis demonstrated radiographic progression free survival at 3,5, and 10 years to be 99%, 95%, and 78% respectively. Pre-GKRS covariates associated with tumorprogression include age great then 65 (p=0.001) and decreasing dose to the margin of the tumor(p=0.05).At last clinical follow-up, 263 patients (91%) demonstrated no change or improvement in theirneurological condition and 27 patients deteriorated (9%). In multivariate analysis, the factorspredictive of new or worsening symptoms were increasing follow up (p=0.01), decreasing maximumdose (p=0.019), tumor progression (p=0.001), and parasellar, clival, or petrous location versuscerebellopontine angle, petroclival or tentorial location (p=0.018).Conclusions: GKRS offers a high rate of tumor control and neurological preservation in patients withskull base meningiomas. More favorable outcomes were observed for those receiving an optimalradiosurgery dose and harboring tumors located in a cerebellopontine angle, petroclival or tentoriallocation.3

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaBE-44Radiosurgery of Benign Intracranial Meningiomas:Factors Associated with Successful TreatmentScott Stafford , Michael J Link, Yolanda Garces, Robert Foote, Bruce PollockMayo Clinic Rochester, Rochester, USAObjective: Radiosurgery of benign intracranial meningiomas is an accepted management option.Proper patient selection is essential to ensure good patient outcomes.Methods: Restrospective analysis of the prospectively acquired Mayo Gamma Knife data base of 417patients (305 women/112 men) having single-fraction SRS for imaging defined (n=251) or confirmedWHO Grade I (n=166) meningiomas from 1990-2008, using the Leksell Gamma Unit. Excludedwere patients with radiation-induced tumors, meningiomatosis, or Neurofibromatosis. The majorityof tumors (n=337, 81%) involved the skull base/tentorium. The mean tumor volume was 9.2 cm3(range, 0.3-48.6); the mean tumor margin dose was 15.9Gy (range, 12-20). The mean follow-up was74 months (range, 6-234).Results: Tumor growth of the irradiated tumor was noted in 11 patients (2.6%) and adjacent to theirradiated tumor (marginal failure) in 13 patients (3.1%). The 5-year and 10-year actuarial localcontrol (LC) rate was 96% and 89%, respectively. Prior tumor resection was associated with a highertreatment failure rate (HR=8.3, 95% CI 2.5-27.8, P

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaBE-52Outcome of large vestibular schwannoma treated withintracapsular decompression or radical resections followedby gamma knife radiosurgery1Hung-Chuan Pan, 1 Ming-Hsi Sun, 2 Dar-Yu Yang1Department of Neurosurgery, Taichung Veterans General Hospital, Taiwan2Department of Neurosurgery, Chang Bing Show Chwan Memorial Hospital, TaiwanObjective: Microsurgery was the mainstay in the treatment of large vestibular schwannoma. However,the outcome of microsurgery was counteracted by the hearing loss and facial nerve dysfunction. Inthis study, we investigate the outcome of intracapsular decompression followed by gamma kniferadiosurgery (GK) compared to the attempted microsurgery followed by GK.Methods: From August 2003 to October 2008, there were 35 patients with large vestibular schwannoma(>3cm in diameter) at least 3 years follow up entering into this study including 18 patients treatedwith intracapsular decompression followed by GK (group I) and 17 patients treated with radical resectionfollowed by GK (group II). Marginal dose of 12 Gy were delivered to residual tumor. All patientsreceived hearing test, electroneuronography (ENoG), SF-36, and MRI periodically. Student’s test andrepeated ANOVA were used for statistical analysis.Results: The age distribution of group I and II were 50 ± 3 and 49±2.3, respectively. The sex distributionof (F/M) were 8/10 and 7/10, respectively. After operation, 16 patients (89%) in group I and 6patients (35%) in group II preserved excellent facial function (p

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaBE-72Radiosurgery for benign tumors of the spine usingthe Synergy S: Clinical experience and future trends1Peter Gerszten, 2 Mubina Quader, 2 Josef Novotny, 3 John Flickinger1Departments of Neurological Surgery and Radiation Oncology, University of Pittsburgh2Department of Radiation Oncology, University of Pittsburgh Medical Center3Departments of Radiation Oncology and Neurological Surgery, University of PittsburghObjective: In distinction to the development of the clinical indications for intracranial radiosurgery,spine radiosurgery’s initial primary focus was and still remains the treatment of malignant disease.The role of stereotactic radiosurgery for the treatment of intracranial benign tumors has been wellestablished. However, there is much less experience and much more controversy regarding the useof radiosurgery for the treatment of benign tumors of the spine. This study presents the clinicalexperience and current trends of radiosurgery in the treatment paradigm of benign tumors of thespine as part of a dedicated spine radiosurgery program.Methods: Forty benign spine tumors were treated using the Synergy S system; 13 cervical, 9 thoracic,11 lumbar, and 7 sacral. Thirty-four cases (85%) were intradural. The most common histologies wereschwannoma (15), neurofibroma (7), and meningioma (8). Eighteen cases (45%) had previouslyundergone open surgical resection. This cohort was compared to our prior institutional experienceof 73 benign spine tumors treated using the CybeKnife.Results: No subacute or long term toxicity occurred (median 26 months). Radiosurgery was used as theprimary treatment in 22 cases (55%) and for recurrence after open surgical resection in 18 cases (45%).The mean prescribed dose to the gross tumor volume (GTV) was 14 Gy (range 11 to 17) delivered in asingle fraction in 35 cases. In 5 cases in which the tumor was found to be intimately associated with thespinal cord, the prescribed dose was 18 to 21 Gy delivered in 3 fractions. No evidence of tumor growthwas seen on serial imaging in any case. Compared to the prior cohort, there was a trend towardsincreased patient age, GTV, and use of radiosurgery in the post-surgical setting, as well as asimultaneous decrease in the prescription dose.Conclusions: Radiosurgery is a safe and clinically effective treatment alternative for benign spinalneoplasms. While surgical extirpation is currently considered to be the best initial treatment optionfor most benign spinal tumors, spine radiosurgery has been demonstrated to have long-term benefitfor such lesions. In a similar manner to which radiosurgery has become a primary treatment optionfor a variety of intracranial benign tumors, radiosurgery may become the most favorable treatmentalternative for similar histologies when found in the spine. The application of radiosurgery fornon-neoplastic spine disease also deserves future investigation.7

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaBE-83The increase of IAC pressure after stereotactic radiosurgeryand hearing outcome of patients with vestibularschwannoma treated with stereotactic radiosurgery:the implication of auditory brainstem response1,3Jung Ho Han, 2,3 Dong Gyu Kim, 2,3 Hyun-Tai Chung, 2,3 Sun Ha Paek, 1,3 Chae-Yong Kim,1,3Chang Wan Oh, 1,3 Young-Hoon Kim1Department of Neurosurgery, Seoul National University Bundang Hospital2Department of Neurosurgery, Seoul National University Hospital3Department of Neurosurgery, Seoul National University College of MedicineObjective: To find out the audiologic and neuro-physiologic evidence that the increase of the internalauditory canal (IAC) pressure is one of the major causes of hearing loss in patients with vestibularschwannoma (VS) treated with stereotactic radiosurgery (SRS) especially using auditory brainstemresponse (ABR). This study was based on the recent reports that IAC pressure correlates well withinterlatency of waves of ABR test, which was proved by direct measurement of the IAC pressure inpatients with VS.Methods: A total of 119 (74.8%) with sporadic unilateral VS and serviceable hearing were treatedwith radiosurgery as a primary treatment and enrolled in this study. The interaural ratio (IAR) andinteraural difference (ID) of each IL I-III and IL I-V were calculated. The larger difference was codedas IAR and ID of between the baseline and the follow-up examination when the patients performedtwo or more ABR examinations within 12 months after SRS.Results: The mean age of the patients was 48±11 years. The mean follow-up duration was 55.2±35.7months (range, 12.3–158). The patients were classified according to the Gardner-Robertson classificationas class (G-R class) 1 in 79 (66.4%) cases. The mean tumor volume was 1.95±2.24 cm3. Themedian marginal dose was 12.0 Gy (range, 11-14). The mean dose to the cochlea was 4.3±1.5 Gy(range, 1.4-8.3).The mean baseline values of IL I-III and IL I-V were 2.58±0.60 mS and 4.80±0.61 mS, respectively.The mean ID-IL I-III and ID-IL I-V were 0.31±0.77 mS and 0.24±0.70 mS, respectively. The meanIAR-IL I-III and IAR-IL I-V were 0.15±0.38 mS and 0.06±0.18 mS, respectively.In the multivariate analysis using the backward stepwise model, the G-R class 2 (p

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaBE-110The relation of treatment parameters to the phenomenon ofvestibular schwannoma swelling after Gamma Knife surgery1Michael Torrens, 1 Christos Stergiou, 1 Pantelis Karaiskos, 2 Alexandra Trampeli, 2 Vasilis Vasdekis1Hygeia Hospital, Athens, Greece2University of Economics and Business, Athens, GreeceObjective: To identify dosimetric factors that predispose to the specific and problematic phenomenonof early swelling of vestibular schwannomas (VS) after radiosurgery.Methods: Information gathered prospectively on 78 patients with VS treated by Gamma Knife 4Cand followed for 2-6 years has been analyzed. 3 patients required a repeat Gamma Knife treatmentbecause of VS swelling. Treatment parameters recorded include data on dosimetry, coverage, Paddickconformity, gradient index, collimator size and number, beam on time, total treatment time (whichincludes APS and helmet change) and source output. Tumour volume was assessed objectively on T2MR images using GammaPlan ® 5.2 both at treatment and follow up. Patients were divided into 2groups - enlarged and controlled. Statistical analysis included the Mann Whitney test and SpearmanRank correlation.Results: Primary volumetric follow up was at 2 years (25.4 ± 2.6 months). At this time 31 (40%)lesions enlarged and 47 (60%) were controlled. On the group analysis using the Mann Whitney test,enlarged tumour volume at 2 years was significantly associated with lower Paddick conformity index(P=0.017), a larger prescription dose (P=0.029) and greater average time per shot (P=0.029). SpearmanRank correlation showed a significant association between enlarged volume and greater averagetime per shot (0.249, P=0.028), smaller size of collimators (-0.277, P=0.014), a lower Paddick conformityindex (-0.299, P=0.008). A trend towards significance was found with a prescription dose of12 Gy rather than 11Gy (0.207, P=0.069), lower age (P= 0.079) and lower source output (P=0.113).Number of collimators, other dosimetric factors, treatment time and % cover were not significantlyrelated to volume change. Factors such as conformity and size of collimators did not change significantlyover the study time.Conclusions: The fact that a greater average time per shot, smaller size of collimators and lowersource output are all associated with the phenomenon of VS swelling suggests that lower dose ratemay be a factor in its genesis, confirming a previous analysis on a smaller series of patients.9

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaBE-141Gamma knife radiosurgery for NF2 associated vestibularschwannomas - The role of higher dose and cochlearimplantation to rehabilitate hearing.1,2Michael Link, 1,3 Bruce Pollock, 2,1 Colin Driscoll, 3 Robert Foote1Dept. of Neurologic Surgery, Mayo Clinic2Dept. of Otorhinolaryngology, Mayo Clinic3Dept. of Radiation Oncology, Mayo ClinicObjective: The purpose of this review was to evaluate the long-term outcome of NF2 associatedvestibular scwannomas (VS) treated with Gamma Knife stereotactic radiosurgery (GKRS). Specifically,we wanted to examine the rate of tumor control, and hearing preservation, and examine the role ofcochlear implantation to rehabilitate hearing in patients after GKRS.Methods: Between 1990 and 2010 32 VS in 26 patients were treated with GKRS. There were 10women. The median age of the 26 patients was 37 years (range: 13 – 68 years). The median clinicaland imaging follow-up was 85 months (range 3 – 253 months).The median marginal dose was 14 Gy (range 12 – 20 Gy) and the median maximum prescribed dosewas 28 Gy (24 – 40 Gy). The median tumor diameter in the posterior fossa was 15 mm (range 6 – 28mm) and the median treatment volume was 2.65 c.c. (range 0.4 – 11.2 c.c.).Four patients have undergone cochlear implantation (CI) following GKRS.Results: After a median follow-up of ~7 years 18 tumors (56%) were smaller with a median tumorreduction of 5 mm. Eight tumors (25%) remained unchanged in size and 6 tumors (19%)were clearly larger compared to the date of radiosurgery and had shown growth on more than onefollow-up MRI scan. The median marginal dose for the tumors that decreased in volume was15.5 Gy and the median marginal dose for the tumors that showed progressive enlargement was13 Gy.Prior to GKRS 13 treated ears had AAO-HNS Class A or B hearing. In 6 patients an “only hearingear” was treated. At last follow-up only 3/13 (23%) kept Class A or B hearing (PTA < 50 dB; WRS >50%).Two of the four patients who received CI following GKRS have had excellent hearing rehabilitation.Reasons for this will be discussed.Conclusions: GKRS for NF2 associated VS provides an opportunity for tumor control at higher dosesthan usually recommended for sporadic VS but is a poor hearing preservation strategy. However, CIfollowing GKRS, when performed soon after treatment and before a long duration of deafness mayresult in good hearing rehabilitation.10

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaBE-162Radiosurgery of lower cranial schwannomasYoshihisa Kida, Toshinori Hasegawa, Takenori KatohKomaki City HospitalObjective: Long-term follow-up results of stereotactic radiosurgery for lower cranial schwannomas inand around the jugular foramen are reported.Methods: The subjects of this study were 33 patients with lower cranial schwannomas, 11 males and22 females, and their mean age was 47.0 years. Large tumors in the posterior fossa as well as tumorsin the upper cervical region were treated first by surgical resection. In two cases, upper cervical tumorswere removed by a transcervical approach, and the residual tumor in and around jugular foramen wascurrently treated by radiosurgery. The mean diameter of the schwannomas was 25.0 mm (10.3 cc inmean volume), and they were treated with mean maximum dose of 26.1 Gy and mean marginal doseof 13.3 Gy.Results: Tumor control was achieved in all cases and the estimated response rate (tumor shrinkage)was 70%. Neurological deficits attributable to motor nerve dysfunction, including hoarseness andswallowing disorders, improved in 16 cases (48.5%) and disappeared in another 5 cases (15%) inthe mean follow-up period of 70 months after the radiosurgery. Meanwhile, 12 cases (36%) wereunchanged without showing any progression. No clear adverse effects were identified.Conclusions: From both a radiological and functional standpoint, lower cranial schwannomas can betreated successfully by radiosurgery to achieve an excellent outcome, especially when tumors growand extend into the jugular foramen. Among intracranial schwannomas, motor nerve ones like lowercranial and facial nerves showed a best response in terms of tumor control as well as functional recoveryafter radiosurgery, which is much better in quality than that of surgical resection.11

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaBE-163Beyond the ten thousand: experiences ofthe Sheffield Gamma Knife unitAndras Kemeny, Matthias Radatz, Jeremy RoweNational Centre For Stereotactic Radiosurgery, SheffieldObjective: Review of 25 year experience with Gamma Knife technology.Methods: Since its installation in 1985 the Gamma Knife unit in Sheffield has treated 11,310 patients.Retrospective analysis of the prospectively maintained database, supplemented by disease-specificretrospective case-note review was carried out.Results: The steadily increasing annual treatment numbers provided immense opportunities toacquire large experience in the management of the common indications (over 5000 AVMs, over2500 vestibular schwannomas, over 1000 meningiomas etc). This resulted in dramatic changes in themanagement paradigms for vestibular schwannomas in the UK and there are encouraging signs thatthe same is happening for meningiomas. This large practice also offered deeper understanding of theresponse to radiosurgery of rare pathologies e.g. pineal tumours, trigeminal neuromas, phacomatosesand a large series of over 100 glomus jugulare tumours. The particular commissioning (reimbursement)arrangements in the United Kingdom have resulted in peculiarities of case-mix, particularly inwithholding treatment for many patients with metastases.Conclusions: Despite the unchanged principle of gamma knife structure, the developing technologyand particularly the evolving radiological support has offered an increasingly precise and tailoredtreatment. This paper will analyse the effects of these changes upon the treatment delivery andoutcome.12

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaBE-205Gamma knife radiosurgery inhibit progression of vestibularschwannoma with pre-treatment evidence of growth-aretrospective long term follow up studyTheresa Wangerid, Petter FöranderKarolinska University Hospital, Department of Neurosurgery, Stockholm, SwedenObjective: Gamma knife radiosurgery (GKRS) has for the last decades been an established alternativetreatment for patients with vestibular schwannoma (VS). Studies of patients treated with GKRS for VSshow tumor control (TC) rate in 90-97%. Epidemiological studies have shown that a large proportionof the VS are stationary when followed conservatively with repeated magnetic resonance images(MRI). The implication of these results could be that most VS are in no need for intervention. A majordrawback with many of the existing studies is short follow up times. This study will investigate thelong-term effect of GKRS on VS and evaluate the chance of growth inhibition after treatment of VSwith pre-treatment evidence of growth.Methods: We reviewed a cohort of 128 patients, 62 men and 66 women, with VS who had consecutivelybeen treated with GKRS at Karolinska University hospital between 1997-2003. Patients previouslytreated for VS, patients from abroad and patients with neurofibromatosis were excluded fromthe study. Mean age at time of treatment was 64 years (23-89). Patients were followed clinically fora median time of 96 months (11-165) and radiologically for 84 months (5-170). 5 patients were lostto follow up. 4 patients underwent GKRS for a second time. 6 patients had microneurosurgery due toprogressive tumor growth.Results: TC was achieved in 92% of patients after GKRS. Pre-treatment growth of VS was notcorrelated to rate of TC, strongly indicating that GKRS inhibit further growth of VS. 12 patientshad loss of TC, 10 were re-treated either with surgery (6 patients) or with GKRS (4 patients). Newtreatment with surgery or GKRS was performed in median in 49 months from the first treatment. Nocorrelation was noted between tumor size, age or gender of the patients and tumor control rate. 3%had trigeminal symptoms and 4% of the patients had facial nerve palsy after treatment.Conclusion: This study concludes excellent tumor control rate in patients with VS treated with GKRSin long time follow up. The tumor control results are not dependent on the pre-treatment growth, orvolume of the tumor.13

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaBE-228Gamma knife radiosurgery for central neurocytomas:A long-term follow-up study1,2Hidfumi Jokura, 1 Jun Kawagishi, 1 Kazuyuki Sugai, 1 Kou Takahashi, 2 Teiji Tominaga1Jiro Suzuki Memorial Gamma House, Furukawa seiryo Hospital2Department of Neurosurgery Tohoku University School of MedicineObjective: It is widely acknowledged that surgical total removal is the golden standard for the treatmentof central neurocytoma, but sometimes it can be difficult with acceptable risk. We evaluatedthe efficacy and safety of gamma knife radiosurgery (GKRS) as an adjuvant therapy for central neurocytoma.Methods: Consecutive eight patients with central neurocytoma treated by GKRS between May 1996and April 2009 are included in this study. All but one patient had undergone partial to gross totalremoval. In one case, GKRS was the first treatment and diagnosis was based on MRI. GKRS was performedfor recurrence or regrowth of residual tumor in 5 cases and for residual tumor in 2 cases. Themean interval between surgical removal and gamma knife was 31.8 months. The volume of tumor atthe time of GKRS was 1.6-7.6 cm3 (mean 4.8 cm3). The median prescribed marginal dose was 15Gy(12-22Gy). Follow-up MRI and clinical information was available in all patients. The mean periodbetween GKRS and the last follow-up MRI was 104 months (ranging from 27 to 169 months) and in4 patients the period exceeded 10 years.Results: The tumors within the target volume shrunk or almost disappeared in all cases at the lastMRI follow-up. In one patient, the tumor recurred outside of the target volume together with unilateralhydrocephalus and needed second GKRS 54 months after the first GKRS. In this patient, regressionof both tumor and hydrocephalus were confirmed 4 moths after second GKRS. In one patient,ventriculo-peritoneal shunt had been placed 3 months after GKRS for hydrocephalus that had existedat the time of GKRS. No radiation-induced complication was noted in any of the patients during thefollow-up period. The KPS scores at the last follow-up was maintained or improved in all patients.Conclusion: GKRS for central neurocytoma is a powerful and safe adjuvant therapy when completesurgical removal with acceptable risk is difficult.14

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaBE-276The Barrow Neurological Institute Experience withstereotactic Radiosurgery for Vestibular Schwannomas:single vs. Multiple Fraction and Hearing Outcomes.Randall Porter, Peter Weisskopf, Mark Syms, Phil DaspitBarrow Neurological InstituteObjective: Vestibular schwannomas (VS) are benign tumors of the cerebellopontine angle. Their treatmenthas evolved with radiosurgery playing an increasing role. As such, an emphasis on cranial nervepreservation has been pursued. Hearing preservation rates have historically ranged from 40-90% at3 years. Fractionation has been an important treatment strategy to preserve other cranial nervefunction such as the optic nerve. Therefore, fractionated radiosurgery has been suggested as a treatmentstrategy to preserve hearing in patients with VS. We sought to compare the single fraction(SFRS) with hypo-fractionated radiosurgery (HFRS) at a single institution with respect to hearingoutcomes in patients with acoustic neuromas.Methods: VS treated with stereotactic radiosurgery (SRS) using either SFRS or HFRS from 1997through 2011 at the Barrow Neurological Institute. All GammaKnife patients were treated withSFRS, and most Cyber Knife patients were treated with HFRS.Results: We treated 386 patients with vestibular schwannomas. We excluded those patients with lessthan six months of follow-up, those with NF2 and those without both pre- and post-treatment audiograms.The study sample consisted of 210 patients: 94 HFRS and 116 SFRS. Mean age was 55 yearsfor HFRS and 62 years for SFRS (p =0.001). Statistical significance was found between groups withthe SFRS group being older. Prior resection occurred in 19.8% of the HFRS group and 29.3% ofSFRS group (p=0 .129). Mean tumor volume (cc) in HFRS was 2.78 and SFRS of 2.28 (p=0.222). Atlast follow-up, hearing was preserved in 38% of SFRS and 61% HFRS (p=0 .019). The hearing preservationrate was higher in those with AAO grade A prior to SRS; 52% of SFRS and 74% of HFRSsubjects (p=0.161). Tumor volume had no impact on hearing preservation (p= 0.154). Resectionfreetumor control was found in 97.7% of HFRS subjects and 98.4% of SFRS subjects. Regressionanalysis found HFRS statistically significant in hearing preservation (p= 0.004, OR 4.426, 95% CI,1.587-12.347).Conclusions: HFRS appears to have superior outcomes compared with SFRS with respect to hearingoutcomes when VS are treated with stereotactic radiosurgery.15

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaBE-298Radiosurgery for Pineal Tumours: Lessonsfrom a Single Unit’s Experience1Jeremy Rowe, 1 John Yianni, 2 Nader Khandanpour, 1 Gabor Nagy,2Nigel Hoggard, 1 Matthias Radatz, 1 Andras Kemeny1National Centre for Stereotactic Radiosurgery, Sheffield, UK.2Dept Radiology, Royal Hallamshire Hospital, Sheffield, UK.Objective: Pineal tumours present management dilemmas. This reflects their varied histology, andthe hazards of surgical approaches. These issues prompted a systematic review of our radiosurgicalexperience to rationalize future therapeutic choices.Methods: From 1987-2009, 44 patients (66% male) underwent 50 Gamma Knife radiosurgicaltreatments. Mean(±SD) age at first radiosurgery was 34±16 years. Twenty-four patients had definitivehistology (11 pineal parenchymal tumours(PPT), including 2 pineoblastomas, 6 pineocytomas and 3 ofintermediate differentiation; 6 astrocytomas, 3 ependymomas, 2 papillary epithelial tumours, 2 germ celltumours(GCT)). Eleven patients had undergone surgery without a definitive tissue diagnosis: nine hadnot undergone surgery. Ten patients had received radiotherapy (5 PPT, 3 astrocytomas, 2 without tissuediagnosis).At treatment, mean tumour volume was 3.7±3.5cm3. Mean marginal dose was 18±4Gy.Mean follow-up was 62±53months (range 6-240). Radiological features were assessed blindly by tworadiologists.Results: Of 44 patients, five died 36±37 months after radiosurgery. Five further individuals showedradiological disease progression. Seven of these 10 patients had received radiosurgery as salvagetherapy. Malignant tumour histology (p=0.04), previous radiotherapy (p=0.002) and radiologicalevidence of necrosis (p=0.03) were associated with poor outcomes. Patients with none of thesefeatures had a 5 year progression free survival of 91% (80% at 10 years). If any of these featureswere present, the 5 year progression free survival fell to 48%. No complications were identifieddue to radiosurgery.Conclusions: Patients referred for radiosurgery are clearly super-selected. GCTs are under-representedin this series reflecting their established and effective treatment paradigms, and clearly they need to beidentified with blood/CSF markers and biopsy as appropriate. The finding that a quarter of this seriesdid not have a tissue diagnosis despite undergoing surgery, raises the question of how far it is mandatoryto pursue tissue diagnoses. The high control rate if no worrying features are present, combined with thelack of complications, suggests that primary radiosurgery without a tissue diagnosis is justifiable. Oncethere are concerns of malignancy, necrosis or failed radiotherapy, we suspect that a tissue diagnosis isessential, as these patients are often young and their response to radiosurgery less certain.16

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaBE-304Risk factors for recurrences after Gamma Knife radiosurgeryof intracranial meningiomas3Vincent Bulthuis, 1,2 Patrick Hanssens, 1,2 Suan Te Lie, 4 Fons Kessels, 1,3 Koo van Overbeeke1Gamma Knife Center, St Elisabeth Ziekenhuis, Tilburg, The Netherlands2Department of Neurosurgery, St Elisabeth Ziekenhuis, Tilburg, The Netherlands3Department of Neurosurgery, Maastricht Universitair Medisch Centrum, Maastricht,4Department of Clinical Epidemiology and MTA, Maastricht Universitair Medisch CenObjective: Gamma Knife radiosurgery (GKRS) is a well established treatment for intracranial meningiomas.Regrowth of treated tumors occurs in about 10% of the patients. Apart from histopathologyas a known risk factor for regrowth, the importance of other patient, tumor or treatment planningrelated factors, like involving the dural tail in the plan, are not clearly defined. We reviewed the resultsof our center to access the risk factors for regrowth of mengiomas after GKRS.Methods: Between June 2002 and April 2008, 246 patients with 297 meningiomas were treated in ourcenter. The median tumor volume was 4,5cc. Median follow up period was 61 monthsThe dural tail was not included in the treatment plan.Based on the diagnosis of a meningioma, 2 groups were distinguished:Group A: There were 115 patients with 118 meningiomas without previous treatment. The diagnosiswas based upon defined MRI-characteristics.Group B: 131 patients with 179 meningiomas had surgery prior to the first GKRS. 125 (69.8%)tumors were classified as WHO I, 49 (27.4%) as WHO II and 5 (2, 8%) as WHO III.Results: Group A: Progression of 7 of 118 meningiomas resulted in a overall local control rate of93,9%.No significant risk factors for progression were indentified.Group B: In 26 of 179 meningiomas progression was documented. For WHO grade I meningiomasthe overall local control rate was 90,1%.In WHO grade II and III meningiomas, the overall recurrence rate was 46, 7%.Risk factors indentified in this group were: (1) WHO II/III histology, (2) prior surgery with additionaltreatment, (3) >1 meningioma treated in one session.No tumor recurrences were seen at the dural tail.Conclusions: No histological verification is needed to treat benign meningiomas with GKRS whenMRI criteria are respected. Tumor histology is a known risk factor for regrowth which is confirmedin this study. In our study, the dural tail was not involved in the treatment plan. No recurrences wereseen at the dural tail. In our opinion it is not necessary to involve the dural tail in the treatment plan.17

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaBE-306Preliminary Results after Multisession Gamma KnifeRadiosurgery for Perioptic Meningiomas.1Alberto Franzin, 1 Piero Picozzi, 1 Marzia Medone, 2 Antonella Del Vecchio, 3 Angelo Bolognesi,4Stefania Bianchi-Marzoli, 1 Camillo Ferrari da Passano, 1 Pietro Mortini1Dept. of Neurosurgery and Radiosurgery IRCCS S. Raffaele, Università Vita-Salut2Dept. of Medical Physics, IRCCS San Raffaele, Università Vita-Salute, Milano, I3Dept. of Radiation Oncology, IRCCS S. Raffaele, Milano, Italy4Dep. Of Ophthalmology, IRCCS San Raffaele, Università Vita-Salute Milano, ItalyObjective: To evaluate the effectiveness and safety of a Gamma Knife treatment in three consecutivedays (multisession) in patients with parasellar meningioma in close contact to the optic nerve andchiasm.Methods: Between January 2006 and September 2010 49 patients (41 females, 8 males, mean age 57years) underwent multisession gamma knife treatment at San Raffaele Hospital for a meningioma inclose contact to the optic nerve and chiasm. Five patients have been treated for optic nerve meningioma,44 for a parasellar meningioma. Preoperative decreased visual acuity or visual fields defect wasfound in 28 patients. Gamma Knife radiosurgery was delivered in three sessions with a mean prescriptionisodose of 6.8 Gy per session (range 6.5-7 Gy) and a mean total prescription isodose of 20.7Gy (range 19.5-21 Gy). Mean tumor volume was 8.8 ml (median 7.6, range 0.33-34.2). Maximumdose to the optic apparatus was always below 7 Gy for each session (mean 5 Gy).Results: Median follow-up was 29.5 months (range 6-57). Overall tumor control rate was 100%.Tumor volumetric reduction was observed in 33 patients (67%), whereas in 16 patients (33%) novolumetric change was recorded. No patient experienced worsening of visual function, in 5 patients(10%) visual acuity improved after treatment; visual field improvement occurred in 4 patients (8%).Cranial nerve function improvement was recorded in 2 patients (4%); one patient experienced VIcranial nerve paresis (2%).Conclusion: This preliminary experience suggests that multisession radiosurgery with Gamma Knifecan be a safe and effective treatment for tumors immediately adjacent to segments of the opticapparatus.18

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaBE-308Gamma Knife Radiosurgery for GrowthHormone-Secreting Pituitary Adenoma1Alberto Franzin, 1 Marco Losa, 1 Piero Picozzi, 1 Giorgio Spatola, 2 Angelo Bolognesi, 1 Micol Valle,1Lorenzo Gioia, 1 Pietro Mortini1Dept. of Neurosurgery and Radiosurgery, IRCCS S. Raffaele, Università Vita-Salu2Dept. of Radiation Oncology, IRCCS S. Raffaele, Milano, ItalyObjective: Single-session radiosurgery with Gamma Knife (GK) may be a potential adjuvant treatmentin acromegaly. We analyzed the safety and efficacy of GK in patients who had previously receivedmaximal surgical debulking at our hospital.Methods: The study was a retrospective analysis of hormonal, radiological, and ophthalmologic datacollected in a predefined protocol from 1994 to 2009. The mean age at treatment was 42,3 years(range 22-67 yrs).One hundred and three acromegalic patients, 62 women and 41 men, participatedin the study. The median follow-up was 71 months (interquartile range 43–107 months). All patientswere treated with GK for residual or recurrent GH-secreting adenoma.Results: Sixty-three patients (61.2%) reached the main outcome of the study. The rate of remissionwas 58.3% at 5 years (95% CI 47.6– 69.0%). Other 15 patients (14.6%) were in remission after GKwhile on treatment with somatostatin analogues. No serious side effects occurred after GK. Eight of102 patients (7.8%) experienced a new deficit of pituitary function. New cases of hypogonadism,hypothyroidism, and hypoadrenalism occurred in 4 of 77 patients (5.2%), 3 of 95 patients (3.2%),and 6 of 100 patients at risk (6.0%), respectively.Conclusions: In a highly selected group of acromegalic patients, GK treatment had good efficacy andsafety. This may lead to reconsider the role of GK in the therapeutic algorithm of acromegaly.19

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaFU-62Neuromodulation in Gamma Knife Surgery forFunctional Disorders: Current and Future1,2Motohiro Hayashi, 1 Noriko Tamura, 1,2 Shoji Yomo, 1 Manabu Tamura,1Masahiro Izawa, 1 Mikhail Chernov, 1 Yoshikazu Okada1Tokyo Women’s Medical University2Saitama Gamma Knife Center, Sanai Hospital, Saitama, JapanObjective: Gamma knife surgery (GKS) has been applied as a treatment for functional disorders, andthe clinical results are preferable and acceptable to be evaluated. However, the critical action mechanismis not known yet. Among of them, we suspected it should be destructive change due to GKS fortremor and epilepsy caused by hypothalamic hamartoma. On the other hand, we also suspected thatintractable pain and mesial temporal lobe epilepsy(MTLE) might not be triggered by the destructivechange according to postoperative clinical course. We will report our clinical results to demonstrateneuromodulative change which might provide the patients cure.Methods: 130 patients with essential trigeminal neuralgia(TGN), 21 patients with cancer pain(CP),24 patients with thalamic pain syndrome(TPS), and 4 patients with MTLE were registered in ourretrospective study. All patients could be followed up at least 3 years excluding the cases with cancerpain. In TGN, the target should be the trigeminal nerve at retrogasserian region with 90Gy at maximumdose using single shot of 4 mm collimator. In CP and TPS, the target should be the anterior lobeof the pituitary gland with 140-180Gy at maximum dose using single shot of 8 mm collimator. InMTLE, the target should be the archeocortex and entrhinal cortex, whose target volume should beranged between 7 and 8cc, with 22-24Gy at marginal dose using 4 and 8 mm collimators.Results: In TGN, 98% of initial electric discharge free, 66% of complete pain free at the last followup, and 24% of significant complication (facial numbness). In CP, 90.5% of significant pain reductionwithout significant complication. In TPS, 71% of significant pain reduction without significantcomplication excluding 30% of endocrinological impairment. In MTLE, 75% of significant seizurecessation without significant complication excluding MR morphological changes were seen.Conclusions: The true action mechanism of these presenting disease could not be elucidated yetwithout some hypothesis that GKS might provide something of neuromodulative effect to the patients,according to postoperative clinical phenomena. We would like to have much more experience andperform basic research to prove our hypothesis.20

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaFU-92Gamma knife radiosurgery for trigeminal neuralgia 2002-20101Rosario Musella, 1 Robert Miller, 1 Kent Larsen, 2 Lloyd Pettegrew1Bayfront Medical Center2University of South FloridaObjective: This study evaluated the effectiveness of pain relief in patients treated with gamma knifesurgery (GKS) for trigeminal neuralgia (TN).Methods: Seventy eight patients with typical clinical symptoms of TN were treated with GKS. Allpatients received 50-90 Gy using a single 4 mm shot. Pain relief was classified as excellent (no pain,off medication), good (no pain with medication), fair (tolerable pain with medication), poor (severepain despite medication).Results: At the last follow-up (range 3-90 months) pain control was classified as excellent in 29%,(22) good in 25% (19), fair in 9% (7), and poor in 36% (29) of the patients. Of the whole group,27% (21) described some numbness but it was only symptomatic in 9% (7). Predictors of favorableoutcome included: long history of the disease, one versus multiple branches involved, and age olderthan 70. None of these characteristics, however, achieved statistical significance. Women had astatistically significant better outcome than men (p < .004). Dose escalation beyond 85 Gy was notassociated with improved outcome and resulted in higher incidence of sensory dysfunction. Of thosepatients who initially responded but relapsed, 21 (28%) were retreated and achieved a better responserate than those treated only once but with a higher incidence of numbness.Conclusion: Stereotactic GKS is an effective treatment in patients with TN.It is suggested that 85 Gy represents the dose that is associated with best pain control and the leasttoxicity. Patients who respond initially but have a recurrence of pain may be retreated with favorableresults but with more toxicity.21

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaFU-121Evaluation of Outcomes in Gamma Knife StereotacticRadiosurgery in Treatment of Trigeminal Neuralgia2Alyssa Zemanek, 1,3 Peter Shin, 1,2 Randy Sorum, 1,2 Michael McDonough, 1,2 Kenneth Bergman,1,2Dean Mastras, 1,2 Kevin Sanders, 1,2 Nathan Bittner, 1,2 Ann Pittier, 1,2 Herbert Wang1South Sound Gamma Knife, Tacoma, USA2Tacoma/Valley Radiation Oncology Centers, Tacoma, USA3South Sound Neurosurgery, Tacoma, USAObjective: It is well documented that stereotactic radiosurgical lesioning of the trigeminal nerve entryis an effective treatment of trigeminal neuralgia [TN], and an appealing alternative to invasive treatments.This study details the outcomes of 79 cases.Methods: This study consisted of a retrospective chart review of 79 cases in 73 patients treated withGamma Knife stereotactic radiosurgery (GKSRS) at our facility. A single 4 mm shot of 75-85 Gy forprimary treatment and 50-70 Gy for secondary treatment was delivered with the Leksell GammaKnife 4C to the trigeminal nerve 4 to 7 mm from its origin from the brainstem while limiting theradiation dose to the brainstem to the 20% isodose line. Of those 79 cases, seven were secondaryGKSRS treatments. Two patients had been lost to follow-up, leaving 71 patients available for analysis.Results: Median follow-up was 30 months. Mean dose administered for primary treatment was 79.4Gy (range, 75-85Gy); for secondary treatment it was 57.1 Gy (range, 50-70Gy). A total of 91.2% ofpatients undergoing their first GKSRS experienced pain relief following treatment at a median of 30days post -treatment. Of this population, 32.3% of patients experienced a recurrence of symptoms,at an average of 11 months after treatment. No significant differences were found between outcomesof subgroups including patients with multiple sclerosis, atypical TN, or those who had undergoneprevious surgical treatment for TN. There was no difference in outcome between the doses administered(75, 80, and 85Gy). For those patients receiving their second GKSRS for TN, there was an initialsuccess rate of 71.4% with 40% of that population eventually having recurring symptoms.Overall, 32.3% of patients developed some level of facial numbness. Of patients greater than 3 yearspost-treatment, (n=21), 52.4% experienced numbness, indicating a possible trend that this side effectmay increase over time.Conclusions: This study contributes to the growing body of research advocating that Gamma Knifestereotactic radiosurgery is an effective treatment of TN. Patient outcomes in terms of success of treatmentare comparable to other studies. No significant predictor of recurrence or failure was found.22

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaFU-124A comparative study of gamma knife radiosurgery andpercutaneous retrogasserian glycerol rhizotomy fortrigeminal neuralgia in multiple sclerosis patients.David Mathieu, Khaled Effendi, Mario Séguin, Jocelyn BlanchardDepartment of Surgery, Division of Neurosurgery, Université de Sherbrooke, CentrObjective: Patients with multiple sclerosis (MS) present a high incidence of trigeminal neuralgia (TN),and the outcomes after treatment seem inferior than in patients suffering from idiopathic TN. Thegoal of this study was to evaluate the clinical outcomes after gamma knife radiosurgery (GKRS)compared to percutaneous retrogasserian glycerol rhizotomy (PRGR).Methods: We retrospectively reviewed the charts of 45 patients with MS-related TN. GKRS was thefirst procedure in 27 patients, and PRGR in 18. Pain had been present for a median of 60 months(12-276) and 48 (12- 240) for patients receiving both procedures, respectively. The following outcomemeasures were assessed: pain relief (using the BNI scale), procedural morbidity, time to pain relief andrecurrence, and subsequent procedures performed.Results: The median follow-up length was 39 months (13-69) in the GKRS group and 38 months(2-75) in the PRGR group. Reasonable pain control (BNI grades I to IIIb) was noted in 22 (81.4%)and 18 patients (100%) after GKRS and PRGR, respectively. The median time to pain relief was 204days for GKRS, and immediate relief in all PRGR patients. In the GKRS group, 17 patients requiredsubsequent procedures (3 for absence of response and 14 for pain recurrence) compared with 7 inthe PRGR group (all for recurrence). At the last follow-up, complete or reasonable pain control wasfinally achieved in 23 (85.2%) patients in the GKRS group and 16 (88.9%) patients in the PRGRgroup. The morbidity rate was 22.2% in the GKRS group (all sensory loss and paresthesia) and66.7% in the PRGR group (most being hypalgesia, with 2 patients having corneal reflex loss and onepatient suffering from meningitis).Conclusions: GKRS and PRGR are both satisfactory strategy for multiple sclerosis related TN withsimilar long-term pain outcome. GKRS has lower sensory and overall morbidity than PRGR, butrequires a delay before pain relief occurs. We propose that patients with extreme pain who need fastrelief undergo PRGR. For other patients, GKRS seems to be an appropriate first-line managementmodality.23

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaFU-143Evaluation of Outcomes in Gamma KnifeStereotactic Radiosurgery Treatment ofEssential and Parkinsonian Tremor1Alyssa Zemanek, 1,2 Randy Sorum, 2,3 Peter Shin, 1,2 Herbert Wang, 1,2 Michael McDonough,1,2Kenneth Bergman, 1,2 Kevin Sanders, 1,2 Nathan Bittner, 1,2 Ann Pittier, 1,2 Dean Mastras1Tacoma/Valley Radiation Oncology Centers, Tacoma, USA2South Sound Gamma Knife, Tacoma, USA3South Sound Neurosurgery, Tacoma, USAObjective: The purpose of this study was to examine the outcomes of 39 patients (40 cases) withessential or Parkinsonian tremor who were treated with Gamma Knife stereotactic radiosurgery(GKSRS) via ventralis intermedius (Vim) thalamotomy.Methods: A total of 40 cases of tremor were treated at our institution, 35 essential tremor, threeParkinsonian tremor, and two with both types of tremor. Using magnetic resonance imaging, theVim was located and treated, receiving a single isocenter exposure of 130Gy with a 4-mm collimator.These patients were followed by their radiation oncologist or neurosurgeon. A retrospective reviewof medical records, in combination with patient phone interviews, was conducted to obtain data ontreatment outcomes.Results: In total, 39 patients with a median age of 77.5 years, received GKSRS for tremor. They hada median pre-treatment tremor duration of 13 years (range, 1.5-70). With a median follow-up periodof 15.5 months (range, 3-64), a total of 33 patients (82.5%) responded to the treatment, as evidencedby lessening in their tremor severity. Of these patients, 24% had a complete response, with no residualtremor. The median time to response was 3.5 months (range, 0.1-12). One patient developed unilateralweakness in his lower extremity with evidence of significantly more edema than what is considerednormal. He had steroid and physical therapy that resolved this weakness.Conclusions: GKSRS Vim thalamotomy at our institution was shown to provide relief from tremor atrates similar to other studies on this topic. This is a viable, safe and effect treatment option that is analternative to deep brain stimulation in patients refractory to medication.24

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaFU-146Gamma Knife radiosurgery for trigeminal neuralgiasecondary to megadolichobasilar artery: a prospective seriesof 29 cases with more than one year of follow up1Constantin Tuleasca, 1 Romain Carron, 2 Noémie Resseguier Resseguier, 3 Anne Donnet, 1 Jean Régis1Functional and Stereotactic Neurosurgery Clinic& Gamma Knife Unit, Marseille2Department of Public Health and Medical Information, CHU Timone, Marseille3Department of Neurology, Clinical Neuroscience Federation, MarseilleObjective: This study analyses prospectively the long term results of Gamma Knife surgery (GKS) inorder to consider its potential role in nowadays armamentarium as treatment for trigeminal neuralgiasecondary to megadolichobasilar artery (MBA).Methods: Between December 1992 and November 2010, 33 consecutive patients presenting with ITNsecondary to MBA were operated by GKS and followed prospectively in Timone University Hospital.The follow up is at least of 1 year in 29 patients. The median age was 74.90 years (min 51; max 90).The GKS typically was performed using MR and CT imaging guidance and a single 4 mm isocenter. Themedian of the prescription dose (at the 100%) was 90 Gy (min 80; max 90). The target was placed onthe cisternal portion of the V-th nerve. Clinical and dosimetric parameters were analyzed. GKS was thefirst surgical procedure in 23 patients (79.31%).Results: The median follow- up period was 46.12 months (12.95 to 157.93). All the 29 patients (100%)were initially pain free in a median time of 13.5 days (0, 240). Their probability of remaining pain freeat 0.5, 1, 2 years was 93.1%, 79.3% and 75.7% respectively, attending at this moment the flat partof the curve. Seven patients (24.13%) experienced a recurrence with a median delay of 10.75 months(3.77, 12.62). The actuarial rate of recurrence was not higher than in our population with essential TNalthough atypical pain was associated with a much higher risk of recurrence (HR= 6.92, p= 0.0117).The hypoesthesia actuarial rate at 0.5 years was 4.3% and at 1 year reach 13% and remains stable till12 years with a median delay of onset of 7 (5, 12) months. Female patients had a statistically muchlower probability of developing a facial numbness (p of 0.03). No patient reported a bothersomehypoesthesia.Conclusion: Retrogaserian high dose GKS turned out to be very safe with only 13.04% hypoesthesia,which was never disabling (0%) while achieving high quality pain control. The majority of the patientsdemonstrated a prolonged effect of radiosurgery in absence of any trigeminal nerve disturbance.25

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaFU-151Gamma Knife Surgery for Hemifacial Spasm Related toCerebellopontine Angle Tumors1,2,5Chuan-Fu Huang, 1,2,4 Cheng-Siu Chang, 1,4 Hsien-Tang Tu, 1,3,4 Wen-Shan Liu1Gamma Knife Center2Department of Neurosurgery3Department of Radiation Oncology4Chung-Shan Medical University Hospital, Taichung, Taiwan5China Medical University Hospital, Taichung, TaiwanObjective: Most of tumor-related hemifacial spasm (HFS) reported was treated by open surgery. Wereport the effect of GKS on benign tumor-related HFS at a follow-up of 84 months.Methods: From 2000 to 2011, a total of 6 patients with cerebellopontine tumors (4 meningiomas, and2 schwannomas) with HFS underwent GKS as a primary treatment. These patients had tumors withinthe radiosurgical target area. For meningiomas, the mean radiosurgical treatment volume was 5.3 ml(range 1.2-9.2 ml), and the mean radiosurgical tumor margin dose was 14.1Gy (range 12-18 Gy); for 2schwannomas, the volume was 2.5 ml and 11.2 ml, and the marginal dose was 12 Gy. Five patients werefemale and one male. The mean duration of HFS was 15.5 months (range 3-36 months). The mean ageat the time of radiosurgery was 52.7 years (range, 45-60 years).Results: The mean follow-up period was 84 months (range 40 to 110 months). Overall, 4 of 6 patients(66 %) experienced complete HFS relief without medication after GKS and one patient had a goodoutcome. The mean time of the improvement was 7 months (range 2 to 18 months). Only one patienthad failed relief of HFS and coincidentally this tumor size was not shrunk. For all 6 patients (100%),there was tumor growth control at a mean follow-up of 56 months after GKS, four of them had tumorsize decreased and two were not changed. Two patients with facial numbness reported improvementafter tumor shrinkage.Conclusions: GKS appears to be an effective tool to treat benign tumor related HFS and control tumorgrowth. Reduction of tumor volume is related to spasInm improvement.26

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaFU-196Comparison reports: Thalamotomy, GK thalamotomy,DBS for Parkinsonian tremor patientsMooseong KimInje University Busan Paik Hospital, Busan, KoreaObjective: Tremor, either essential tremor or Parkinsonian tremor, has been effectively and safely treatedby GKS or RF lesioning or DBS the ventral intermediate(Vim) nucleus of the thalamus with or withoutmicroelectrode recording. The authors evaluate the treatment outcome of sixteen tremor patients whohad been treated with thalamotomy without microelectrode, five parkinson’s disease with Gamma Knife,five parkinson’s disease with DBS.Methods: Between September, 2001, and December, 2011, sixteen tremor patients were treated withthalamotomy without microelectrode recording. Twelve patients suffered from Parkinsonian tremor andfour patients were essential tremor patients. The male to female ratio was 1.6 to 1 with median age of59.6 years (range; 39-74 years). Under local anesthesia, a 3mm hole was made using a hand-held twistdrill, and the dura mater was penetrated with a 1.2mm sharp drill beat. Radiofrequency(RF) electrodewas placed in the Vim nucleus of thalamus. With intraoperative macrostimulation, RF lesion was made.Five parkinson’s disease tremor patients were operated with bilateral Vim-DBS. Five parkinson’s diseasetremor patients were operated with unilateral Vim-GK thalamotomy. A radiation dose of 120 Gy wasdelivered to nucleus using a single 4 mm collimator plug pattern following classic anatomical landmarks.Preoperative and postoperative tremor was evaluated with simple tremor severity scale, UnitedParkinson’s disease Rating Scale tremor score(UPDRS) and the development of complications relatedwith the procedure was closely reviewed at the immediate postoperative period and the last follow-up.Results: RF thalamotomy produces immediate relief in up to 98.4% of the patients. There were nodevelopment of complications related with procedure, all patients discharged one or two days aftersurgery. In DBS surgery patients ,Tremor was completely abolished in 40 % in patients, almost abolishedin 60 %. There was no complications. GK thalamotomy patients produced an excellent improvement oftremor in four patients, mild improvement in one patient.Conclusions: Vim thalamotomy without microelectrode recording is a safe and effective procedure tocontrol the tremor with minimal morbidity. DBS is very beneficial in treating bilateral intractable tremorpatients.Intraoperative macroelectrode stimulation safely localizes the Vim nucleus target of the thalamus for thetreatment of patients with tremor. GK thalamotomy is for intractable unilateral tremor patients withmedical disease, severe old age, coagulopathy,etc. Unilateral Vim GK thalamotomy is very effective forintractable tremor patients and contralateral side treated with Vim-DBS27

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaFU-231Gamma knife thalamotomy for Parkinson’sdisease and essential tremor: A prospectivemulti-institutinal study in Japan1Yoshinori Higuchi, 2 Chihiro Ohye, 2 Toru Shibazaki, 3 Takao Hashimoto, 3 Toru Koyama,4Tatsuo Hirai, 5 Shinji Matsuda, 6 Toru Serizawa, 7 Tomokatsu Hori, 7 Motohiro Hayashi,7Taku Ochiai, 8 Hirofumi Samura, 8 Katsumi Yamashiro1Department of Neurological Surgery, Chiba University Graduate School of Medicine2Functional and Gamma Knife Surgery Center, Hidaka Hospital, Takasaki, Japan3Center for Neurological Diseases, Aizawa Hospital, Matsumoto, Japan4Gamma Knife Center, Heisei Memorial Hospital, Fujieda, Japan5Gamma Knife House, Chiba Cardiovascular Center, Ichihara, Japan6Tokyo Gamma Unit Center, Tsukiji Neurological Clinic, Tokyo, Japan7Department of Neurosurgery, Tokyo Womenâ€s Medical University, Tokyo, Japan8Department of Neurosurgery, Okinawa Central Hospital, Naha, JapanObjective: No prospective study of gamma knife thalamotomy for intractable tremor has previouslybeen reported. To clarify the safety and optimally effective conditions for performing unilateral gammaknife (GK) thalamotomy for tremors of Parkinson’s disease (PD) and essential tremor (ET), a prospectivemulti-institutional study was conducted by JLGK society (JLGK0301).Methods: In total, 72 patients (tremor dominant PD, n = 59; ET, n = 13) were registered at six institutes.Following our selective thalamotomy procedure, the lateral part of the ventralis intermediusnucleus, 45% of the thalamic length from the anterior tip, was selected as the isocenter. A single 130Gy shot was applied using a 4-mm collimator. During the follow-up study, patients were examinedat intervals of 3, 6, 12, 18 and 24 months postoperatively. Evaluation included neurological examination,magnetic resonance imaging and/or computerized tomography, the unified Parkinson’s diseaserating scale (UPDRS), electromyography, medication change and video observations.Results: Final clinical effects were favorable. Of 53 patients who completed 24 months of follow-up,43 were evaluated as having excellent or good results (81.1%). Notably, UPDRS scores showedtremor improvement (Parts II and III). Based on tremor scores of UPDRS Part III for the treatedside, 58.1% of the PD patients and 60% of ET patients had score 0 (no tremor). Marked change inrigidity was statistically significant; however, gait and slow movement showed no significant changeduring follow-up. Thalamic lesion size fluctuated but converged to either an almost spherical shape(65.6%), a sphere with streaking (23.4%) or an extended high-signal zone (10.9%). No permanentclinical complications were observed.Conclusions: GK thalamotomy is an alternative treatment for intractable tremors. Less invasiveintervention may be beneficial to patients.28

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaFU-259Meta-analysis of gamma knife treatmentfor trigeminal neuralgia1,2José Lorenzoni, 2 Adrián Zárate, 1 Raúl De Ramón, 1,3 Leonardo Badinez,1Francisco Bova, 1 Claudio Lühr1Centro Gamma Knife Santiago, Gamma Knife Chile2Departamento de Neurocirugía, Pontificia Universidad Católica de Chile3Departamento de Radioterapia, Fundación Arturo López PérezObjective: To analyze the results published in the literature concerning Gamma Knife treatment fortrigeminal neuralgia focused on pain outcome, side effects and prognostic factors.Methods: A search in PubMed and Medline was performed looking for publications meeting thekeywords: trigeminal neuralgia, radiosurgery and Gamma Knife. Only clinical series were selected,excluding systematic reviews. When many publications from the same center were found, only the mostrecent was considered.The data studied were the latency for pain improvement, the initial pain response, the long-term paincontrol, treatment-related morbidity and prognostic factors for pain outcome. Pain control was assessedby the Barrow Neurological Institute Pain Scale (BNI) and long term pain control was evaluatedconsidering actuarial methods. Prognostic factors associated with pain outcome were classed as clinical,anatomo-radiological and dosimetric.Only significant prognostic factors in multivariate analysis were considered. For each variable threestudies were done. First, a study of the number of publications supporting the positive, neutral ornegative influence on pain outcome, then, a study considering the number of patients included in suchstudies and finally an integrated analysis of the hazard ratios.Results: Sixty one manuscripts published between 1997 and August 2011 were selected for thepurpose of this study. The mean latency period for pain control was 4.5 weeks (range 1.5 to 10), themean initial pain control for BNI I to BNI III (pain well controlled with or without medications) was86%. At five years the mean actuarial pain control was 54%. The average of sensory disturbanceswas communicated in 21.5%, (6.7% numbness or bothersome). Sensory dysfunction was morefrequent after repeated Gamma Knife treatment.The most consistent prognostic factors for better pain control were: absence of previous treatments,typical trigeminal neuralgia, absence of multiple sclerosis, irradiation dose ≥ 80 gray and post-treatmenthypoesthesia.Conclusions: Gamma knife treatment is a safe and useful modality for the treatment of trigeminalneuralgia with an initial adequate response in 86% and long-term pain control in one half of patients,comparable to other ablative treatments. Some prognostic factors for pain outcome were systematicallyidentified.29

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaMA-34Delayed Radiation-Induced Vasculitic Encephalopathy:A Histopathological Correlation for Adverse RadiationImaging Effects after Radiosurgery1Veronica Chiang, 2 J.P.S Knisely, 3 A Vortmeyer1Yale School of Medicine, New Haven, CT2Yale School of Medicine, New Haven, CTObjective: Delayed diffuse leukoencephalopathy is a well-known complication of standard fractionatedexternal beam radiation therapy to the brain.Single fraction, high dose, focused radiation therapysuch as Gamma Knife radiosurgery is being increasingly used for the treatment of metastatic cancerto the brain to avoid such diffuse injury. However, adverse radiation effects (ARE) on MRimaging arenow also being reported in up to half of metastatic lesions treated with radiosurgery and are thoughtto also represent delayed leukoencephalopathy. While radiosurgery-induced leukoencephalopathy isknown to be clinically different than that following fractionated radiation, the pathological differencesare not well characterized. We retrospectively reviewed the radiographic and histopathological findingsin cases of surgically resected ARE to understand radiosurgery-induced leukoencephalopathy. Novelfindings are reported.Methods: We examined the histopathological tissue of 10 patients whose brain metastases had beenpreviously treated with Gamma Knife radiosurgery. In all of these patients, surgical management ofa symptomatic regrowing lesion was subsequently required. Given the surgical accessibility of theselesions, all were removed en bloc at Yale New Haven Hospital between January 1, 2009 and June 30,2010. All specimens showed no evidence of tumor recurrence upon thorough review of their histopathology.The clinical and magnetic resonance imaging data for each of the 10 patients were then reviewed.Results: The patients in this study all presented with progressively growing contrast-enhancing lesionson follow-up magnetic resonance imaging 8 to 17 months after Gamma Knife treatment, whichprompted surgical resection of the affected area. Neuropathologic examination revealed absenceof residual or recurrent tumor, but marked leukencephalopathic changes, including demyelination,coagulation necrosis and vascular sclerosis. In addition, abundant inflammatory cells were notedthroughout the parenchyma, which were mostly CD3+ T lymphocytes. Unexpectedly, small andmedium-sized vessels also showed a marked transmural T cell infiltrate indicative of active vasculitis.Conclusions: In this study involving 10 patients who received Gamma Knife stereotactic radiosurgicaltreatment for brain metastases, we provide evidence that radiation-induced leukoencephalopathy maypresent as a rapidly advancing process that grows to extend beyond the original high-dose radiationfield. We hypothesize that a vasculitic process in association with radiation leukoencephalopathy mayfacilitate the progressive nature of the condition.30

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaMA-43Long Term Evaluation of Optic Nerve Dose and RadiationOptic Neuropathy in Gamma Knife RadiosurgeryScott Stafford, Jacqueline Leavitt, Michael Link, Bruce PollockMayo Clinic Rochester, Rochester, USA.Objective: To determine the long-term risk of radiation-related optic neuropathy (RON) in patientshaving Gamma Knife radiosurgery (GKRS) for benign skull base tumors.Methods: From 1991-1999, 222 patients underwent GKRS for confirmed WHO Grade 1 orpresumed meningiomas (n=143), pituitary adenomas (n=72) or craniopharyngiomas (n=7).Excluded were patients with prior external beam radiation therapy. Prior surgery was performedin 129 patients (58%). Dose planning was performed using MRI in all cases. A median of 9isocenters (range, 1-29) were used to treat a median tumor volume of 5.9 cm3 (range, 0.1-30.4).The median tumor margin dose was 18 Gy (range, 12-30). The maximum radiation dose to theoptic chiasm and nerves was initially calculated by interpolation of isodose curves on the anteriorvisual pathways (AVP) (1991-1993), then maximum point dose determination (1994-1999) usingGamma Plan. Maximum AVP dose: ≤ 8.0 Gy (n=126), 8.1-10.0 Gy (n=39), 10.1-12 Gy (n=47),> 12 Gy (n=10). The mean clinical and imaging patient follow-up was 83 months (range, 4-238)and 123 months (range, 8-237), respectively.Results: In these patients with up to 19 years of follow-up, one patient (0.5%) developed RON.This patient had undergone prior surgery and had documented optic atrophy before GKRS.Eighteen months after GKRS she developed unilateral visual field loss; the AVP dose was12.8 Gy. The risk of RON for patients receiving > 8 Gy to the AVP was 1.0%.Conclusions: Patient selection, conformal dose planning and appropriate dose prescription arenecessary to achieve tumor control at a low risk of RON. Selected cases can be treated safelywith maximum AVP doses of 10-12Gy with low risk of developing RON.31

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaMA-59Effect of HER2/neu overexpression status onmultidisciplinary treatment modalities includingupfront or adjuvant GKS for women with breastcancer brain metastasis1Xu Zhiyuan, 1 Chun-Po Yen, 2 David Schlesinger, 1 Jason Sheehan1Gamma Knife Center, Department of Neurosurgery, University of Virginia, USA2Department of Radiation Oncology, University of Virginia, USAObjective: To study the influence of HER2/neu overexpression status on efficacy of multidisciplinarytreatment modalities including upfront or adjuvant GKS for brain metastases arising from breast cancer.Methods: We retrospectively reviewed records of a total of 103 patients diagnosed with breast cancerand brain metastases treated at University of Virginia Gamma Knife Center between 1996 and 2011.Kaplan-Meier plot with log rank test was employed to estimate the survival time and the difference.Cox proportional hazards regression models were utilized to determine prognostic factors as follows:age at primary malignancy diagnosis, age at CNS metastasis, ER, PR, HER2/neu status, number andtotal volume of CNS metastases, initial distant metastasis at sites including lung, liver, bone, andbrain, time interval between development of CNS metastases and GKS, primary breast cancer diagnosisand CNS metastases.Results: Median age at diagnosis of initial breast cancer was 45 years (range, 24 – 81, mean±SD,46.1±11.0). Median time interval from breast cancer diagnosis to CNS parenchymal metastasis was 36.5(0 – 368) months. There were 43 patients (41.7%) identified as HER2/neu+, 60 (58.3%) were HER2/neu-. All HER2/neu+ patients received Herceptin or Tykerb during the course of treatment. Overall survivalafter diagnosis of CNS metastasis was 27 months and 17 months in HER2/neu+ and HER2/neusubgroups,respectively (p=0.006). Survival benefit after diagnosis of CNS metastasis was demonstratedin patients with WBRT and adjuvant GKS as compared with GKS alone (median survival: 23 vs. 14months, log rank test, p=0.04). Multidisciplinary treatment modalities conferred substantially extendedsurvival evidenced by median survival times in a decreasing sequence: surgical resection plus WBRT andGKS, surgical resection plus GKS, WBRT plus GKS, and GKS alone (p=0.009). On multivariate analysis,the HER2/neu+ status and KPS at CNS metastasis greater than 70 remained independent predictors ofsurvival after adjusting for other important clinicopathologic factors.Conclusions: HER2/neu overexpression status plays an important role in predicting survival benefitafter diagnosis of CNS metastasis. In patients treated with upfront GKS, there was survival advantagein HER2/neu+ subgroup as compared with HER2/neu- one. Breast cancer brain metastasis patientsbenefit from the multidisciplinary treatment.32

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaMA-67Validity of the Diagnosis-Specific Grading indexes forRadiosurgically-Treated Patients with Brain Metastasesfrom Breast CancerMasaaki Tamamoto, Takuya Kawabe, Bierta E. Barfod, Yoichi UrakawaKatsuta Hospital Mito GammaHouseObjective: Very recently, two diagnosis-specific grading indexes for patients with brain metastases(METs) from breast cancer were proposed; Diagnosis-Specific Graded Prognostic Assessment (DS-GPA, by Sperduto PW et al in Int J Radiat Oncol Biol Phys 2010;77:655-64) and Breast CancerRecursive Partitioning Analisis (BC-RPA) Prognostic Index (by Nimińska A et al in Int J Radiat OncolBiol Phys 2011 May 17[Epub ahead of print]). We assessed whether the two indexes are valid forselecting patients with brain METs for gamma knife radiosurgery (GKS).Methods: A total of 269 consecutive female patients (mean age; 55 [range; 26-86] years) in RPA ClassI (n = 37, 14%), II (213, 79%) and III (17, 6%) formed the basis of this retrospective study. A totalof 211 patients (78%) harbored multiple tumors (median tumor numbers; 5 [range; 1-69]). The meanclinical follow-up period was 14.9 (range; 0.2-138) months.Results: Kaplan-Meier analysis demonstrated that the overall median survival time (MST) was 9.0months: 17.1/8.4/2.7 months for RPA class I/II/III (p = 0.007 for I vs II and p=.0464 for II vs III).However, MSTs were 28.2/11.4/7.2/4.9 months for the DS-GPS groups of 3.5-4.0/3.0/1.5-2.5/0-1.0(p=.1747 for 3.5-4.0 vs 3.0, p=.1561 for 3.0 vs1.5-2.5 and .467 for 1.5-2.5 vs 0-1.0). Also, MSTswere 9.0/9.7/0.8 months for the BC-RPA classes I/II/II (p = 0.9358 for I vs II and p

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaMA-68A retrospective study of GKRS-treated MET patients:Tumor numbers of two-four versus five or moreMasaaki Tamamoto, Takuya Kawabe, Bierta E. Barfod, Yoichi UrakawaKatsuta Hospital Mito GammaHouseObjective: The role of stereotactic radiosurgery for brain MET patients with tumor numbers (TNs) offive or more is not fully understood.Methods: Among our consecutive series of 2502 patients with brain METs, who underwent GKRSduring the 1998-2011 period, 1775 (740 females, 1035 males, mean age; 65 [range; 19-92] years)with TNs of two or more (median; 5, maximum; 89) were chosen for this retrospective study. Originaltumor most-commonly stemmed from the lung (1183 patients, 66.6%), followed by breast (214,12.1%), lower alimentary tract (109, 6.1%), upper alimentary tract (67, 3.6%), kidney (60, 3.9%),other organs (110, 6.2%) and unknown (34, 2.0%). Among the 1775 patients, 796 had TNs of twofour(group-A) and the other 975 of five or more (group-B).Results: Median survival time (MST) after GKRS was significantly longer in group-A (7.4 months)than in group-B (5.9, p

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaMA-73What is the best grading system in stereotactic radiosurgeryfor brain metastases, RTOG-RPA, SIR, BSBM, GPA or a modified RPA?1Toru Serizawa, 2 Osamu Nagano, 3 Yoshinori Higuchi, 2 Shinji Mastuda, 2 Junichi Ono,3Naokatsu Saeki, 1 Tatsuo Hirai, 4 Msaaki Yamamoto1Tokyo Gamma Unit Center, Tsukiji Neurological Clinic, Tokyo, Japan2Gamma Knife House, Chiba Cardiovascular Center, Ichihara, Japan3Department of Neurological Surgery, Chiba University, Chiba, Japan4Katsuta Hospital Mito GammaHouse, Hitachinaka, JapanObjective: A new index for Recursive Partitioning Analysis (RPA) classification of patients with brainmetastases proposed by Masaaki Yamamoto was applied to our patient series for comparison withpreviously established systems including the original RPA, score index for SRS (SIR), basic scorefor brain metastases (BSBM) and graded prognostic assessment (GPA), in order to ascertain whichgrading system is the best for gamma knife surgery (GKS).Methods: Twenty-two hundred and forty-six patients with brain metastases, treated by the first authorwith GKS during the 1998-2010 period at Chiba Cardiovascular Center and Tsukiji NeurologicalClinic, were analyzed.Results: There were 1341 men and 895 women. Median age was 65, range 7-94. Extracranial diseasestatus was judged to be “controlled” in 281. Median tumor numbers were 3, range 1-100. The mostcommon primary site was the lung (1490 cases), followed by gastro-intestine (277), breast (230),uro-genital (136) and others (113). There were 133 (MST 24.8Mo) RPA class I, 1812 (7.8) II and301 (3.6) III cases, with statistically significant differences (p

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaMA-81Prognostic factors for Gamma Knife Radio-surgery in patientswith ≥5 brain metastasesLilyana Angelov, Alireza M. Mohammadi, Robert Weil, Samuel Chao, Nicholas Marko,Michael Vogelbaum, John Suh, Gennady Neyman, Gene BarnettRose Ella Burkhardt Brain Tumor and Neuro-Oncology Center Cleveland Clinic USAObjective: Gamma-Knife radio-surgery (GK) is one of the mainstays of treatment in patients withbrain metastases, especially for 4 or fewer lesions. Currently there is an increasing interest in offeringthis treatment modality to patients with a more extensive intracranial burden of disease (≥5 metastases)as an upfront treatment or in combination with whole brain radiation therapy (WBRT). However,data is lacking specifically related to the outcomes and prognostic factors in this subgroup of patients.In this study, prognostic factors contributing to overall survival (OS) of patients with ≥5 brain metastaseswere evaluated.Methods: An IRB approved retrospective review of 170 patients with ≥5 brain metastases treated atthe Cleveland Clinic GK Center (1997-2010) was performed. Patient demographics, tumor characteristics,treatment related factors as well as outcome of treatment were evaluated. Statistical analysiswas performed using Kaplan-Meier survival summaries and Cox proportional hazards regression.Results: Patient median age was 58 and female/male ratio was 94/76. The most common primary siteswere lung 84(49%) and breast 34(20%). At the time of GK, 70(41%) of the patients had multipleextracranial metastases, and KPS was ≥90 in 66(39%) of patients. Most of the patients 135(79%)were recursive partitioning analysis (RPA) class II and median graded prognostic index (GPA) was1.5. Median total intracranial disease volume was 3.25cc(range 0.19-37.19cc) with a tumor volumeof ≥10cc in 32(19%) of patients. Median number of lesions was 6(range 5-20). Median OS after GKwas 6.8 months. At the time of GK, older age, lower KPS, extensive extracranial disease burden,higher RPA class, lower GPA, non-lung primary pathology, and higher total intracranial tumor volumewere statistically significant poor prognostic factors using univariate analysis. Multivariate analysisdemonstrated lower KPS, multiple extracranial metastases and higher intracranial tumor volume weresignificant negative prognostic factors.Conclusions: In this large series of GK treated patients with ≥5 brain metastases, OS was significantlyimproved in patients with higher KPS and without extensive systemic involvement. Further, the totalintracranial disease burden was more relevant than the actual number of lesions. This data suggeststhat GK should be considered an appropriate treatment modality in the management of multiple brainmetastases.36

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaMA-96Survival and complications following Gamma Kniferadiosurgery or enucleation for ocular melanoma:a 20-year experience.1Eduard B. Dinca, 2 Daniel Preotiuc-Pietro, 1 John Yianni, 1 Matthias W.R. Radatz,1Jeremy Rowe, 3 Paul Rundle, 1 Andras A. Kemeny1The National Centre for Stereotactic Radiosurgery, Sheffield, UK2Department of Computer Sciences, University of Sheffield, UK3Department of Ophtalmology, Royal Hallamshire Hospital, Sheffield, UKObjective: We present our experience in treating ocular melanoma at the National Centre forStereotactic Radiosurgery in Sheffield, UK over the last 20 years.Methods: We analyzed 170 ocular melanoma patients treated with Gamma Knife radiosurgery,recorded the evolution of visual acuity and complication rates, and compared their survival with 620patients treated with eye enucleation. Different peripheral doses (using the 50% therapeutic isodose)were employed: 50-70Gy in 24 patients; 45Gy in 71 patients; 35Gy in 62 patients.Results: The 5-year survival rates for each group were: 64% for 35Gy, 62.71% for 45Gy, 63.6% for50-70Gy, and 65.2% for enucleated patients. There was no significant difference in survival between the35, 45 and 50-70Gy groups when compared between themselves (p=0.168) and with the enucleationgroup (p=0.454). Clinical variables influencing survival for radiosurgery patients were tumour volume(p=0.014) and location (median 66.4 vs. 37.36 months for juxtapapillary vs. peripheral tumours, respectively;p=0.001) while age and gender did not prove significant. Using 35Gy led to more than 50%decrease in the incidence of cataract, glaucoma and retinal detachment, when compared to the 45Gydose. Retinopathy, optic neuropathy and vitreous haemorrhage were not significantly influenced.Blindness decreased dramatically from 83.7% for 45Gy to 31.4% for 35Gy (p=0.006), as did postradiosurgeryenucleation: 23.9% for 45Gy vs. 6.45% for 35Gy (p=0.018). Visual acuity, recorded up to5 years post-radiosurgery, was significantly better preserved for 35Gy than for 45Gy (p=0.0003).Conclusion: Using a therapeutic dose of 35Gy led to a dramatic decrease in complications, vision lossand salvage enucleation, while not compromising patient survival.37

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaMA-117One-day aspiration/GKS procedure is effective for metastaticbrain tumor with cystic component.Fumi Higuchi, Shunsuke Kawamoto, Keisuke Ueki, Phyo KimDepartment of Neurosurgery,Dokkyo University School of MedicineObjective: GKS is an effective tool for the treatment of metastatic brain tumors. It covers multiplelesions in a single procedure and is less stressful for the patient. However, the tumor size amenable toGKS is limited to less than 3 cm in diameter, and cystic tumors frequently exceed this size limitationeven if the solid portions are small. In order to avoid lowering the prescription dose sufficient for tumorcontrol, the target volume should be decreased as much as possible. For such lesions, we adopted a newstrategy of performing stereotactic cyst aspiration prior to GKS on the same day. We investigated itsefficacy in reducing target volume and tumor control.Methods: Stereotactic aspiration followed by GKS was performed for 26 metastatic brain tumors in25 patients at Department of Neurosurgery Dokkyo Medical University from February 2005 to April2010.Their medical records were retrospectively reviewed. We collected data on target tumor volumesbefore and after aspiration, local control of the tumor and patients’ outcomes.Results: The patient’s ages ranged 32 to 77 years (mean 58). Mean target volume was reduced from20.0 cm3(range 8.0- 64.2 cm3 ) to 10.3 cm3 (range 8.0- 64.2 cm3) after aspiration. Volume reductionwas approximately 50 %. Before aspiration there were 13 lesions exceeding 14 ml in volume, whichis equivallent to a 3cm sphere. In 7 out of these 13 lesions, the target volume was reduced to lessthan 14ml by aspiration. Prescription dose ≥ 20Gy was achievable in all except one case. Follow upperiods were 1-27 months (median11). Seventy-six percent of tumors were well controlled at the endof the follow up or at the patient’s death by other causes. The 1- and 2-year actuarial survival rate was43.1% and 14.4%.Conclusions: One-day aspiration/GKS is effective for brain metastases with cystic component.Aspiration procedure reduces the tumor volume significantly, and thereby warrants satisfactorytumor control by enabling safe delivery of sufficient treatment dose.38

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaMA-133In-depth study of radiation necrosis after Gamma Kniferadiosurgery for brain metastasesPenny Sneed, Joseph Mendez, Igor Barani, Shannon Fogh, Lijun Ma, Michael McDermottUniversity of California, San Francisco (UCSF)Objective: To determine the incidence, time-course, and risk factors for radiation necrosis after stereotacticradiosurgery (SRS) for brain metastases.Methods: Brain-metastasis patients/lesions treated with Gamma Knife SRS September 1998 through2009 were reviewed and excluded for death ≤2 months after SRS or insufficient follow-up (8-month gap in the first year, or inadequate imaging availability). Follow-upimaging was re-reviewed to ensure consistency. Dates of necrosis were recorded, validated by surgicalpathology showing necrosis ± tumor, serial MRI ± perfusion studies, or both. Freedom from necrosisafter SRS was calculated using the Kaplan-Meier method with censoring at last imaging.Results: This study is in progress; full results will be presented. Of 900 patients, ≥363 are eligible;93 died ≤2 months after SRS; 311 had insufficient follow-up; 133 remain to be screened. To date,170 patients with 637 eligible metastases have been fully reviewed, with median survival 17.3 months,median follow-up >2 years in living patients, and median imaging follow-up 8.7 months in censoredlesions. The appearance of necrosis was variable and frequently indistinguishable from tumor progressionat single points in time; serial imaging review was key, along with pathology when available.Overall, 9% of lesions developed necrosis at a median of 8.0 months after SRS (range, 0.9-52.0months; 85% between 3-18 months); another 5% were indeterminate for failure vs. necrosis. Highernecrosis risk was associated with larger target volume, larger maximum diameter, primaries other thanbreast and kidney, and other radiation; 1-year necrosis probabilities were 9%, 12%, 21%, and 37%for SRS performed alone, after prior radiotherapy, concurrent with radiotherapy, or after prior SRS tothe same lesion (p = 0.019). The 1-year necrosis risk was 5% for breast and kidney brain metastasesvs. 18% for other primaries (p = 0.0003), and 4%, 7%, 18%, 36%, and 37% for targets ≤1, 1.1-1.5,1.6-2.0, 2.1-3.0, and >3.0 cm (p < 0.0001). Primary site, other radiation, and diameter all retainedsignificance on multivariate analysis.Conclusions: Necrosis probabilities were higher than expected, particularly for metastases >1.5-2 cm.Other risk factors included non-breast/non-kidney primary, prior or concurrent radiotherapy, andprior SRS.39

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaMA-136Cost-effectiveness of stereotactic radiosurgery versussurgical resection in the treatment of brain metastasis withGerman statutory health insurance perspective4Albertus Van Eck, 1,2 Duong Anh Vuong, 3 Dirk Rades, 4 Gerhard Horstmann, 1 Reinhard Busse1Dept. of health care management, Berlin University of Technology,Berlin, Germany2Dept. of medical service administration, Ministry of health of Vietnam3Dept. of radiation oncology, University Schleswig-Holstein, Luebeck, Germany4Gamma Knife Center Krefeld, Krefeld, GermanyObjective: This study aims to identify the cost-effectiveness of two treatment modalities for the treatmentof brain metastases, stereotactic radiosurgery (SRS) versus surgical resection in combinationwith whole brain Radiotherapy (SR), from the perspective of Germany’s Statutory Health Insurance(SHI) System.Methods: Retrospectively reviewing 373 patients with brain metastases (BMs) who underwent SR(n=113) and SRS (n=260). Propensity score matching (PSM) was used to adjust for selection bias(n=98 each); means of survival time and survival curves were defined by the Kaplan-Meier estimator;and medical costs of follow-up treatment were calculated by the Direct (Lin) method. The bootstrapresampling technique was used to assess the impact of uncertainty.Results: Survival time means of SR and SRS were 13.0, 18.4 months, respectively (P=.000). Mediansof free brain tumor time were 10.4 months for SR compared to 13.8 months for SRS (P=0.003).Number of repeated SRS treatments significantly influenced the survival time of SRS patients (R2=.249; p=.006). SRS had a lower average cost per patient (€7212 - SD: 1047; Skewness: 7273) thanthose of SR (€10964 - SD: 1594; Skewness: 0.465), leading to an incremental cost effective ratio of(ICER) €-8338 per life year saved (LYS), meaning that using SRS costs €3752 less than SR pertargeted patient, but increases LYS by 0.45 years.Conclusions: SRS is definitely a more cost-effective treatment than SR in the treatment of brain metastasis(BM) from the SHI perspective. When the clinical conditions allow it, early intervention withSRS in new BM cases and frequent SRS repetition in new BM recurrent cases should be advised.40

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaMA-172Gamma Knife Radiosurgery for Primary CNS Lymphoma is anIdeal Complementary Therapy1Christopher Duma, 1 Peter Chen, 1 Brian Kim, 1 Maryann Plunkett, 1 Ralph Mackintosh,1Ryan Casserly, 1 Robert Dilman, 1 Ramin Azhir, 1 Brittany Whitely, 2 Alexa Reeves1Hoag Memorial Hospital, Newport Beach, California, USA2University of California Irvine, Irvine, California, USAObjective: Standard therapy for primary CNS lymphoma (PCNSL) currently includes high-dosemethotrexate-based chemotherapy and whole brain radiation therapy (WBRT), but this approach isassociated with significant toxicity, especially neurotoxicity in elderly patients (>age 60 years), whohave a median survival of less than 30 months. For this reason WBRT is increasingly reserved forpatients less than 60 years of age, and older patients are treated with chemotherapy alone. GammaKnife radiosurgery (GKRS) has not been widely used in the management of PCNSL because of thebelief that PCNSL is a multifocal disease. However, GKRS delivers a localized treatment that shouldminimize neurotoxicity, potentially produce better local disease control, and possibly lead to bettersurvival rates than approaches that utilize no RT or WBRT.Methods: Between October 2003 and May 2010 ten PCNSL patients, aged 60 to 84 years, weretreated with GKRS. Doses ranged from 8 Gy to 18 Gy (median: 12) at the 50% isodose line (range:45-85; median 50). Eight of the ten patients had failed chemotherapy prior to GKRS; two patientswere managed with only biopsy and GKRS. Clinical data was gathered for toxicity, disease control,and survival.Results: Side effects attributed to GKRS were minimal; no patients had deterioration in quality oflife related to treatment. All treated lesions demonstrated a partial or complete response on magneticresonance imaging. Only one instance of local recurrence has been observed during 2.5 to 58 monthsof follow up (median followup time 4 years). Median survival is 42 months from initial diagnosis and40 months from GKRS.Conclusions: In patients with PCNSL, GKRS is associated with minimal toxicity and good long-termlocal disease control. In this small series, median survival was over 33% longer than published figuresfor similar patients treated with chemotherapy ± WBRT. Encouraging disease control and survivalcombined with a low incidence of neurotoxicity suggest that GKRS may be a desirable componentof multimodality treatment of PCNSL. Randomized trials would be needed to establish GKRS as acomponent of standard therapy in patients over chemotherapy alone.41

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaMA-173Malignant transformation of low-grade meningiomato high-grade gliosarcoma, six years after gamma kniferadiosurgeryLeon Liem, Brita ChengUniversity of Hawaii, John A. Burns School of Medicine, Honolulu, HIObjective: Gliosarcoma is a rare variant of glioblastoma multiforme. Radiation-induced gliosarcomais rare having been reported in few patients, usually involving high radiation dosages for treatment ofa primary malignancy. Here we report a case in which a patient received single fraction gamma kniferadiosurgery for a confirmed low-grade meningioma and subsequently developed a gliosarcoma sixyears later.Methods: A 50-year-old female presents with progressive confusion, expressive aphasia, right-sidedweakness and ataxia. MRI imaging revealed a very large enhancing mass involving the left lateralventricle and adjacent temporal lobe with extension into the quadrigeminal plate region. The patientunderwent a left parietal craniotomy and a subtotal resection with residual tumor close to thebrainstem. Pathology revealed a well-differentiated meningioma (WHO grade I). The patient receivedpostoperative gamma knife radiosurgery to the residual tumor (14 Gy to the 50% isodose line, tumorvolume 3.4cc with 100% coverage). Yearly MRI imaging revealed stable tumor size with no newsymptomatology.Results: Six years after initial presentation, the patient developed gradual reoccurrence of priorsymptoms and new onset diplopia. MRI imaging revealed an interval increase in tumor mass size withsuperior and inferior extension on the left side of the tentorium, suggestive of recurrent meningioma.The patient underwent a left temporoparietal craniotomy and a subtotal resection with residualinfratentorial tumor. Pathology revealed gliosarcoma (WHO Grade IV) and residual meningioma withradiation-induced changes. The patient declined neurologically and expired 8 months after symptomreoccurrence despite aggressive treatments.Conclusions: Although radiation induced malignancies are well documented, the induction ofmalignant tumors after gamma knife radiosurgery is extremely rare. This case of the developmentof a gliosarcoma after gamma knife radiosurgery for meningioma points out that malignanttransformation is a rare but real concern in the treatment of benign disease.42

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaMA-174A New Measure for the Gamma Knife Radiosurgery Response:The Slope and Plot of Tumor Volume Changes First Evaluatedfor Non-small-cell Lung Carcinoma Brain Metastases.Douglas Kondziolka, Aditya Iyer, Agam Patel, John Flickinger,Hideyuki Kano, Ajay Niranjan, L. Dade LunsfordDepartment of Neurological Surgery, University of PittsburghObjective: Reporting simple tumor volume changes (smaller, no change, larger) after radiosurgery hasbeen used for decades but is inadequate to define the radiobiologic effect. We hypothesized that theslope and appearance of the volumetric response plot would define the radiobiologic effect for specificlesions, radiosurgical techniques, and/or devices. We tested this concept using brain metastases fromnon-small cell lung cancer (NSCLC).Methods: Serial post-radiosurgery MRI images were evaluated in 100 patients who underwentGamma knife radiosurgery between 2006 and 2010 for brain metastases from NSCLC. Patientsreceived between 16 and 20 Gy to the tumor margin. The largest tumor (>1cc) was selected for eachpatient and its volume measured over time using available software. Patients were imaged from 0.4months to 42.4 months following radiosurgery (mean, 9 months).Results: The overall treated tumor control rate was 87%. Eighteen percent of patients had transienttumor enlargement and 9% had sustained tumor growth. Overall, 60% of patients had gradualtumor regression. The reduction in tumor volume occurred most rapidly in the first three monthsfollowing Gamma knife radiosurgery (mean treated tumor reduction = 45%) followed by a less steepdecline in size over the subsequent two years (mean reduction = 32% after 3 months). At each intervalthe reduction was as follows: 3 months=45%, 6 months=47%, 9 months =55%; 12 months=64%,15 months=66%, 18 months=75%, 21 months= 81%, 24 months=77%.Conclusions: The tumor volume response after Gamma knife radiosurgery is dynamic; the reductionin tumor volume is most pronounced in the three month interval after radiosurgery. The slope andappearance of the response curve will facilitate comparisons with other tumor types, radiosurgicaltechniques or technologies. Shifts of the curve to the left or right will indicate poorer or improvedradiosurgery response profiles.43

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaMA-180Evaluation of mini-mental status examination score obtainedafter using gamma knife radiosurgery as the initial radiationtreatment for brain metastasesKiyoshi NakazakiDepartment of Neurosurgery, Brain Attack Center Ota Memorial HospitalObjective: This study aimed to evaluate (1) the mini-mental status examination scores (MMSEs) ofpatients with brain metastases, after they underwent gamma knife radiosurgery (GKS) without wholebrainradiation treatment (WBRT) and (2) the factors influencing MMSEs.Methods: Between January 2009 and June 2011, all patients with new brain metastases, i.e., 119patients, were treated using 1 session of GKS without WBRT as initial radiation therapy. MMSEswere determined for all patients before GKS and for the surviving patients at every 3 months afterGKS.Results: We could evaluate 76 patients (63.9%) after GKS. The median age, number of brain metastases,and total volume of brain metastases were 65.5 years (range, 40–92 years), 2 (range, 1–18), and4.17 ml (range, 0.04–27.0 ml), respectively. The median values for marginal dose, total skull integraldose, and MMSE follow-up time were 22.0 Gy (range, 14–24 Gy), 2.9 joules (range, 0.1–9.6 joules),and 5.8 months (range, 0.9–21.6 months), respectively.Thirty-nine patients (51.3%) developed newdistant lesions after the first GKS. The median survival time with or without follow-up MMSEs was8.8 and 2.8 months, respectively.The median pre-GKS MMSE in cases where follow-up MMSEs were obtained was 28 (range, 3–30).Thirty-eight patients (50.0%) had a pre-GKS MMSE of 3 points and those of 15 patients (19.7%) deteriorated by >3 points. For 4of these 15 patients, the cause of deterioration was not directly related with brain metastases; for 4of the remaining 11 patients, the deterioration in MMSEs recovered to within 3 points. The 6- and12-month actual free rates of the 3-point drop in the MMSEs were 83.9% (47 of 56 cases) and 79.2%(19 of 24 cases), respectively. Larger tumor volume was associated with an improvement of >3 pointsin the follow-up MMSE. No risk factors were significantly associated with a deterioration of >3 pointsin the follow-up MMSEs.Conclusion: GKS stabilizes neurocognitive function with less adverse effects. The mental deteriorationof patients with large symptomatic metastatic tumors tends to decrease after GKS.44

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaMA-182Gamma knife radiosurgery for brainstem metastasesTakuya Kawabe, Masaaki Yamamoto, Bierta E Barfod, Yoihi UrakawaKatsuta Hospital Mito GammaHouse, Hitachi-naka, JapanObjective: The efficacy of gamma knife radiosurgery (GKRS) for brainstem metastases (METs) isnot yet fully understood. We retrospectively studied our database of patients with GKRS-treatedbrainstem METs.Methods: In total, 200 patients (79 women, 121 men, mean age; 64 [range; 36-86] years) whounderwent GKRS at our facility between July 1998 and April 2011 were analyzed. The most commonprimary site was the lung (136 patients) followed by the gastrointestinal tract (24), breast (18), kidney(12) and others (10). Among a total of 222 tumors, lesion location was the pons in 120, the midbrain in66 and the medulla oblongata in 36. The mean and median tumor volumes were 1.3 and 0.2 (range;0.005-10.7) cc, the median peripheral dose 18.0 (range; 12.0-25.0) Gy.Results: The overall median survival time (MST) was 6.0 months. MSTs according to RecursivePartitioning Analysis (RPA) were 9.4 months in Class 1 (20 patients), 6.0 in Class 2 (171) and 1.9 inClass 3 (nine). Better KPS and single metastasis were significant factors favoring survival. Neurologicaland qualitative survival rates were 95.0% and 88.0% at the 6th post-GKRS month and 91.4% and84.3% at the 12th post-GKRS month, respectively. Follow-up imaging studies were available for 129patients (65%). The tumor control rate was 91.1 % at the 6th post-GKRS month, 64.3% at the 12thpost-GKRS month.Conclusions: Our present results suggest GKRS to be effective for brainstem METs.45

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaMA-183Gamma knife radiosurgery for brain metastases fromgastrointestinal tract cancersTakuya Kawabe, Masaaki Yamamoto, Bierta E Barfod, Yoichi UrakawaKatsuta Hospital Mito GammaHouse, Hitachi-naka, JapanObjective: Brain metastases (METs) from gastrointestinal (GI) tract cancers are relatively uncommon.We evaluated the efficacy of Gamma Knife radiosurgery (GKRS) for brain METs from GI tract cancers.Methods: Among our consecutive series of 2,550 patients who underwent GKRS for brain METs atthe Katsuta Hospital Mito GammaHouse during the 13-year period from July 1998 to July 2011,301 (11.8%) patients (92 women, 209 men, mean age; 65 [range; 25-88] years) with METs from GItract cancers were selected for this study. The most common primary tumor site was the colon (101patients) followed by the rectum (96), stomach (66), esophagus (39), duodenum (three) and smallintestine (two). Mean and median lesion numbers were 4 and 2, respectively, range 1-37. The medianvolume of the largest tumors was 6.7 (range; 0.02-55.6) cc, and the median peripheral dose was 20(range; 10-25) Gy. The median period between original cancer diagnosis and brain MET occurrencewas 23 (range; 0- 237) months. The median KPS at the time of GKRS was 80% (range 40-100%).Results: The median survival time (MST) was 5.1 months overall. MSTs according to RecursivePartitioning Analysis (RPA) were 16.9 months in Class 1 (7 patients), 5.7 in Class 2 (255) and 2.2in Class 3 (39). Single metastasis, better KPS, synchronous metastasis and well-controlled primarytumors were significant factors favoring survival. Neurological survival and qualitative survivalwere 94% and 83% at the 6th post-GKRS month and 90% and 70% at the12th post-GKRS month.Follow-up imaging studies were available in 185 patients (61%). The tumor control rates and newlesion-free survival rates per patient were 84% and 45% at the 6th and 69% and 34% at the12thpost-GKRS month.Conclusions: Our present results suggest GKRS to be effective for GI tract cancer brain MET patientsof RPA classes 1 and 2.46

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaMA-187Gamma knife radiosurgery for multiple brain metastases:What is a safe integral dose for the whole skull?Takuya Kawabe, Masaaki Yamamoto, Bierta E Barfod, Yoichi UrakawaKatsuta Hospital Mito GammaHouse, Hitachi-naka, JapanObjective: Gamma knife radiosurgery (GKRS) has recently been employed in patients with multiplebrain metastases (METs), even those with five or more lesions. However, very little is known aboutwhole-brain threshold doses, which may have adverse effects on the brain. We attempted to determinesafe integral doses for the entire skull.Methods: We analyzed the treatment protocols of 1,246 GKRS procedures performed for 900 patients(40.3% of cohort) with five or more brain METs (maximum, 89) during the period between January1999 and December 2009. The median lesion number was 10 (range: 5-89) and the median cumulativevolume of all tumors was 7.3 (range: 0.1-115.3) cc. The median selected dose at the lesionperiphery was 20 (range: 10-27) Gy.Results: Integral skull doses were computed using the Leksell Gamma Plan (Elekta AB, Stockholm,Sweden). The median integral skull dose was 8.5 (0.2-28.7) Joules. The median brain volumesreceiving >5 Gy and >12 Gy were 327 (range 5-1942) cc and 50 (range 0-313) cc. Among 578patients (64%) who received less than 10 Joules, none experienced neurological death due to GKRSrelatedcomplications. Among 257 patients (29%) receiving doses between 10 and 15 Joules, onlyone case, who could not receive steroid therapy or undergo surgical removal due to poor systemiccondition, experienced intractable seizures and severe perifocal edema after GKRS. Among 58 patients(6%) receiving doses between 15 and 20 Joules, one experienced gradual brain swelling due tonecrotic change 8 months after GKRS. Among six patients (0.7%) who received over 20 Joules, oneexperienced acute brain swelling 2 days after GKRS.Conclusions: We conclude that integral skull doses of 15 Joules or less are clearly safe, while thoseexceeding 20 Joules carry a relatively high risk of radiation-induced brain injury. The zone betweenlower and higher risk thus appears to be somewhere between 15 and 20 Joules.47

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaMA-232Prospective Multi-institute Study of Gamma KnifeRadiosurgery Alone Treatment for Patients with 1-10 BrainMetastases (JLGK0901): Interim Monitoring Report1Yoshinori Higuchi, 2 Toru Serizawa, 3 Masaaki Yamamoto, 4 Takashi Shuto, 5 Astuya Akabane,6Yasunori Sato, 7 Jun Kawagishi, 8 Kazuhiro Yamanaka, 9 Naokatsu Saeki1Department of Neurological Surgery, Chiba University Graduate School of Medicine2Tokyo Gamma Unit Center, Tsukiji Neurological Clinic, Tokyo, Japan3Katsuta Hospital Mito GammaHouse, Hitachinaka, Japan4Department of Neurosurgery, Yokohama Rosai Hospital, Yokohama, Japan5Gamma Knife Center, Kanto Medical Center, NTT EC, Tokyo, Japan6Chiba University Hospital Clinical Research Center, Chiba, Japan7Jiro Suzuki Memorial Gamma House, Furukawa Seiryo Hospital, Furukawa, Japan8Department of Neurosurgery, Osaka City General Hospital, Osaka, JapanObjective: To present interim monitoring results of the prospective multi-institute study (JLGK0901)of gamma knife radiosurgery (GKRS) for 1-10 brain metastases without whole brain radiationtherapy conducted by the JLGK society.Methods: As of the end of 2010, 819 patients meeting the following 5 major JLGK0901 inclusioncriteria, were evaluated: 1) newly diagnosed, 2) largest tumor less than 3 cm in diameter or 10cc involume, 3) maximum of 10 brain metastases; 4) no more than 15 cc total tumor volume; 5) no MRfindings of CSF dissemination. Primary organs were the lung in 633 patients, breast in 88, colon in 36,kidney in 19, and others in 43. Most cases were RTOG-RPA class II (765 patients, 93.4%), followedby III (28, 3.4%) and I (26, 3.2%).Results: Overall median survival time after GKRS was 0.99 years. The tumor progression-free survival(TPFS) rate was 89.8% at one year. There were statistically significant differences in one-year-TPFSrates among three tumor volume groups, 94.9% in 1576 lesions

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaMA-278Bevacizumab therapy for cerebral radiation necrosis1Manmeet Ahluwalia, 1 Neda Hashemi-Sadraei, 1 Gazanfar Rahmatullah, 2 John Suh, 1 Sam Chao,1Robert Weil, 1 Michael Vogelbaum, 1 David Peereboom, 1 Glen Stevens, 1 Gene Barneet1Burkhardt Brain Tumor and Neuro-Oncology Center, Cleveland Clinic2Taussig Cancer Institute, Cleveland ClinicObjective: Radiation necrosis is a serious complication of radiation treatment for brain tumors.Therapeutic options including steroids, anticoagulation and hyperbaric oxygen have limited efficacy.Radiation necrosis is postulated to be a continuous process involving endothelial cell dysfunction thatleads to tissue hypoxia and necrosis, with secretion of the vascular endothelial growth factor (VEGF).Bevacizumab, an antibody against VEGF had been reported to reduce edema in patients with suspectedradiation necrosis.Methods: After obtaining IRB approval, the Cleveland Clinic Brain Tumor and Neuro-OncologyCenter’s database was used to identify patients with diagnosis of Radiation necrosis on the basisof magnetic resonance imaging (MRI) and/ or biopsy who were treated with bevacizumab between7/2007 and 1/2011.Results: 19 patients with diagnosis of radiation necrosis (4 were biopsy proven) received bevacizumab.Post treatment MRI was performed at an average of 8 weeks after initiating therapy with bevacizumab.Follow-up MRI demonstrated a radiographic response in all patients on the MRI fluid-attenuatedinversion-recovery (FLAIR) sequences and 18 of 19 patients showed improvement in the T1-weightedpost-Gadolinium contrast images. The average area change in the T1-weighted post-Gadoliniumcontrast abnormalities was a decrease of 45.1%, and the average change in the FLAIR images was adecrease of 49.1% (using McDonald’s criteria). Fifteen patients showed clinical benefit. There was amean daily dose reduction of 5.96 mg of dexamethasone after initiation of bevacizumab in patientswho were on steroids at start of bevaciuzmab for radiation necrosis.Conclusions: Bevacizumab appears to produce radiographic response as well as clinical benefit in thetreatment of patients with cerebral radiation necrosis. The improvements can be rapid and bevacizumabis effective in cases that do not respond to traditional corticosteroid therapy.49

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaMA-280Stereotactic radiosurgery of brain metastases in elderlypatients: the cleveland clinic experience1Manmeet Ahluwalia, 1 Neda Hashemi-Sadraei, 2 John Suh, 1 Sam Chao, 1 Lilyana Angelov,1Robert Weil, 1 Michael Vogelbaum, 3 Paul Elson, 1 Gene Barnett1Burkhardt Brain Tumor and Neuro-Oncology Center, Cleveland Clinic2Taussig Cancer Institute, Cleveland Clinic3Quantitative Health Sciences, Cleveland ClinicObjective: Elderly patients often suffer from cerebrovascular impairment. Whole brain radiotherapy(WBRT) can cause vascular damage and enhances the risk of dementia. For patients with a limitednumber of brain metastases (BM) stereotactic radiosurgery (SRS) is promising alternative. This studywas designed to evaluate the therapeutic effect of SRS in patients aged ≥70 years who presented withBM.Methods: The IRB-approved Cleveland Clinic Brain Tumor and Neuro-Oncology Center’s databasewas used to identify patients with BM who were ≥70 years at the time of diagnosis of BM and weretreated with SRS between 8/2000 and 12/2009. Multivariable analysis was conducted to identifyindependent predictors of survival using a Cox proportional hazards model and a stepwise selectionalgorithm with p=0.10 and p=0.05 as criteria for entry and retention.Results: 173 BM patients with a median age of 75 years (range 70-87, 64% male) were included.Most patients had either lung cancer (55%, 95/173) or kidney cancer (16%, 28/173) primaries.Median time between diagnosis of the primary cancer and BM was 10.3 months (0-309.6 months).Forty-six percent (79/173) of patients had multiple BM and 57% (99/173) had extra-cranial metastasesat the time BM was diagnosed. Median overall survival (OS) was 5.5 months from the time of SRS(95% CI, 4.4-7.2 months). Cause of death was extracranial tumor progression in 35% of the patients,cranial tumor progression in only 3%, both cranial and extracranial tumor progression in 9%, andthe cause of death was unknown in 53%.Conclusions: In multivariable analysis, performance status, the interval from diagnosis of the primarycancer to BM, WBRT prior to SRS and presence of extracranial metastasis were all identified asindependent predictors of OS. SRS is a well tolerated and effective treatment for elderly patients.50

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaMA-282Is Ipilimumab effective in melanoma with limited brainmetastasis treated with Gamma Knife procedure?Maya Mary MathewNew York University Langone Medical Center,NY, NY, USAObjective: Brain metastasis in melanoma carries a poor prognosis with an overall survival of 3-5months and minimal response to systemic therapy. Ipilimumab, a human IgG monoclonal antibodyagainst CTLA-4, has shown to improve the survival in patients with metastatic non-CNS melanoma.Its ability to cross the blood brain barrier or as a radiation sensitizer is not clear at this time. Thepurpose of this study was to investigate the efficacy of Ipilimumab in the treatment of metastaticmelanoma with limited brain metastases treated with Gamma Knife (GK).Methods: From 2008-2010, 55 patients with limited brain metastases from melanoma were treatedwith GK procedure. SRS was delivered to a median dose of 20 Gy delivered to 50% isodose line(Range15-20). The median number of lesions treated were 3 (Range 1-8). Ipilimumab was administeredintravenously at 3mg/kg over 90 minutes every 3 weeks for a median of 4 doses (Range1-8) in 23patients. Local control (LC), Progression free survival (PFS) and overall survival (OS) were assessedfrom the date of GK procedure.Results: The median LC, PFS and OS for the entire group were 8, 6 and 5 months respectively. Thecause of death was CNS progression in all but two patients. Salvage therapy was needed in 26(47.3%) patients that included repeat GK in 20 and Whole Brain Radiotherapy in 7 patients. The 6month LC, median PFS and median OS were 62.9%, 5 months and 6 months respectively in patientswho received Ipilimumab and 62.6%, 7 months and 5 months respectively in patients who didn’treceive Ipilimumab ( p=ns). Intracranial hemorrhage was noted in 7 patients who received Ipilimumabcompared to 9 in those who didn’t receive it (p=ns).Conclusions: Administration of Ipilimumab does not appear to affect outcomes in patients withlimited brain metastases who received GK procedure.51

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaMA-284Factors affecting local tumor control in GKRS for METSfrom breast cancer1,2Satoshi Suzuki, 2 Katsuya Ishido1Gamma House, Nippon Steel Yawata Memorial Hospital, Kitakyushu, Japan2Gamma Knife Center, Shin-Koga Hospital, Kurume, JapanObjective: Efficacy of Gamma Knife radiosurgery (GKRS) for patients with metastatic brain tumors(METS) has been mainly evaluated using progression free survival rate or overall survival rate. However,these parameters mainly reflect the patients’ general conditions and do not reflect the local tumorcontrol. Here we focused on the local control ratio of each tumor by GKRS in patients with METSfrom breast cancer.Methods: Two hundred and fifty four patients were treated by GKRS due to METS from breastcancer. The records from 76 consecutive patients who underwent twice or more GKRS for 536 METSwere reviewed to examine the local control of each irradiated tumor. It was defined as failed GKRS(recurrence), if the tumor needs to be re-treated at the next GKRS session.Results: Mean age at the first GKRS was 52 years. The number of METS in each patient was 1-24(average 5). The mean KPS was 80.4. Extra cranial metastases were present in 50% of cases. Fifty %recurrence free probability was 26.9 months. Recurrence was observed in 44 tumors (8.8%).Univariate analysis revealed that factors related to favorable tumor control were, 1) tumor volume1.8mL (equivalent to approximately 1.5cm in diameter) or smaller, KPS less than 70, age 60 or more,2nd or 3rd GKRS, and 4 or more tumors to be treated at the same time. At the 2nd or 3rd GKRS,tumor volume was significantly smaller compared with tumor volume at the 1st GKRS. Tumor volumewas also significantly smaller if the total number of tumor in the patient was 4 or more. Multivariateanalysis revealed that the volume 1.8mL or smaller was the only factor which related to a favorablelocal tumor control.Conclusions: Tumor volume was the only factor which affects the favorable tumor control by GKRSin METS from breast cancer. It is reasonable to treat multiple METS with GKRS as far as the volumeof each tumor is small enough and the integrated dosage delivered onto whole brain is acceptable.52

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaMA-297Early detection of brain metastasis by routine brainscanning in selected cancer patients doubles survivaland increases quality of life1Laura L.E. Ventrella, 2 Nicoletta Cacciari, 1 Enrico Giugni, 1 Federico Rampa, 2 Marta Cubelli,2Sara Quercia, 2 Claudio Zamagni, 1,3 Enrico D.F. Motti1Neurosurgery Dept, Maria Cecilia Hospital, Ravenna, Italy2Medical Oncology Addarii, Policlinico Santâ€Orsola, Bologna, Italy3Neurosurgery, University of Milano, Milano, ItalyObjective: According to the literature 20-40% of cancer patients develop brain metastases (BM).Increasing efficacy of contemporary treatment of the primary tumor with attendant longer survivaltimes and failure of chemotherapy to cross the blood brain barrier (BBB) allow for a relative increaseof metastatic disease to the brain. Even so, due to oncological tradition and imaging costs, follow-upprotocols for lung and breast cancer patients frequently do not include brain scanning. Particularlybreast cancer patients have improved survival due to radio-chemosensibility of their tumors. HER-2positive tumors have better extracranial disease control with Trastuzumab, which does not cross BBB,with higher percentages of BM (50-60%) after one year from diagnosis. Mean prognosis for patientsat diagnosis of BM is 2-4 months; single or combined treatments may increase survival up to 12-15months.We would demonstrate that routine brain scanning, at least in selected cancer patient, increase outcomeafter BM detection.Methods: Among our 5381 Gamma Knife (GK) cases, malignant tumors represents 45%, almost allmetastases (n = 2219). Lung (n = 1144) and breast (n= 377) cancer are the most common primarytumors. We reviewed our cases to evaluate percentage of patient referred that could effectively undergoto GK treatment, outcome, survival and causes of death.Results: The overall survival of patients coming from Centers adopting cerebral follow-up is almostdouble (97 weeks vs. 53), 56% are still alive at 24 months and 25% at 5 years from BM diagnosisand, after six moth, quality of life (Karnofsky) is high, most of patients are free from neurologicalsymptoms and the death for brain causes is exceptional.Conclusions: Early diagnosis allows avoidance of palliative options and offer the most efficienttreatments.Oncological Centers who have adequate routine brain imaging for their breast cancer patients presentmost correct indications to RS and have better results.This means also significantly lower costs for the health care system, which should taken into accountin the financial analysis of protocols allowing early BM diagnosis.53

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaMA-309WBRT usage in patients getting SRS for >5 brain metastases1Jonathan Knisely, 2 James Yu, 2 Veronica Chiang1Hofstra University North Shore-LIJ School of Medicine2Yale University School of Medicine and Yale Cancer CenterObjective: Stereotactic radiosurgery (SRS) of brain metastases improves short-to-intermediate termneurocognitive functioning in patients relative to an approach that combines SRS with whole brainradiation therapy (WBRT) in patients with 1-3 brain metastases. Using SRS alone increases the riskof requiring salvage CNS therapy, but has no impact upon survival, which is commonly held to begoverned by extracranial disease status. WBRT is commonly recommended for patients with >4 brainmetastases, and the appropriateness of SRS alone for this population is questioned. We evaluated acohort of 103 patients treated with Gamma Knife SRS for >5 metastases to identify WBRT usage as acomponent of care for brain metastases.Methods: An institutional review board-approved retrospective analysis of the Yale Gamma Knifedatabase identified patients treated with SRS for >5 brain metastases. WBRT’s use and timing relativeto the dates of SRS and of death were recorded, along with demographic data. Survival was calculatedusing the method of Kaplan-Meier. Cox proportional hazards analysis was performed for variablesassociated with the hazard for death.Results: 103 patients were identified. Lung, melanoma, breast, and kidney primaries were identifiedin 38, 33, 17, and 6 patients, respectively. The remaining 8 patients’ cancers had diverse histologicorigins. 43 patients never got WBRT; 19 were still alive. 24 (56%) died without ever getting WBRT.60 patients had WBRT; 18 were still alive. 45 of these 60 patients (75%) had WBRT prior to SRS for>5 metastases; only 15 (25%) had WBRT after SRS for >5 metastases. The median survival from thedate of radiosurgery for >5 brain metastases was 8.3 months. Overall survival was not impacted byWBRT administration. (p=0.965, HR=0.99 [0.60-1.64].Conclusions: 75% of the patients who got SRS and WBRT had SRS for >5 brain metastases as asalvage therapy despite prior WBRT. Of the 58 patients who got SRS for >5 brain metastases withoutprior WBRT, only 15 (26%) subsequently received WBRT as salvage treatment. WBRT delivery didnot affect overall survival. The neurocognitive sequelae of WBRT may potentially be avoided formost patients with >5 brain metastases.54

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaMA-310Subtraction Fusion With Prior Images Helps IdentifyAdditional Brain Metastases for Repeat Radiosurgery1John Flickinger, 2 Hideyuki Kano, 1 Josef Novotny, 1 Yoshio Arai, 1 Jagdish Bhatnagar,2Ajay Niranjan, 2 L Dade Lunsford, 2 Douglas Kondziolka1Dept. of Radiation Oncology, U. of Pittsburgh School of Medicine2Dept. of Neurological Surgery, U. of Pittsburgh School of MedicineObjective: Identification of all brain metastases present on planning stereotactic images is necessaryto optimize control of brain metastases and limit the need for additional radiosurgery or radiotherapyto the brain. We hypothesized that subtraction fusion of new minus old high-resolution stereotacticcontrast enhanced magnetic resonance (MR) images of brain metastasis patients for radiosurgeryplanning would improve detection of small brain metastases.Methods: We studied 75 patients with 1-6 (median = 1) prior brain metastasis radiosurgery proceduresto 1-55 metastases (median = 4) at the time of subsequent radiosurgery to 1-26 metastases (median=4). Prior high-resolution stereotactic contrast enhanced MR images were co-registered with newimages to identify and outline all prior radiosurgery treatment volumes. All new brain metastases wereoutlined after review by at least one attending Neurosurgeon, one attending Radiation Oncologistand one Medical Physicist. Subtraction-fusion (new minus latest prior) images were constructed andreviewed to see if additional brain metastases could be identified. Two patients had two prior coursesof whole-brain (WB) radiotherapy (XRT), 21 patients had one. 51 had none and one had partial brainXRT. The median interval since the latest prior radiosurgery imaging was 6 months (range: 2-29).Results: Without the subtraction-fusion imaging 0-29 (median=3) new metastases were identified (3patients had radiosurgery only to retreat metastases). After review of the subtraction-fusion (new-old)MR-images 16/75 (21 %) of patients had 1-5 additional brain metastases identified, measuring3-176 cu-mm (median, 15 cu-mm, n=23). Stepwise linear-regression correlated increasing numbersof additional brain metastases identified by subtraction fusion with the total number of new andpreviously identified brain metastases (p=0.001) and prior WB-XRT (p=0.017). Logistic regressioncorrelated an increasing rate of detecting any additional metastases by subtraction fusion with thenumber of previously identified brain metastases (p=0.029).Conclusions: Subtraction-fusion of new minus prior contrast-enhanced high-resolution MR imagesappears to help identify additional brain metastases for radiosurgery planning, particularly with inpatients with greater numbers of brain metastases.55

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaPH-102Clinical Implementation of the Gamma Knife Extend System:A Therapist’s Perspective2Amanda Schoenberger, 3 Robert Dryzmala, 3 Joseph Simpson, 2 Eric Filiput, 2 Christine Bossung,2Karen Watts, 2 Bridget Burke, 2 Barb Kienstra, 2 John Reed1Gamma Knife Center of Saint Louis2Barnes-Jewish Hospital3Washington University Medical SchoolThe Extend System, a non-invasive stereotactic Gamma Knife Perfexion accessory, permits fractionatedand sub-cranial treatments. The technique is useful when treating larger targets in previouslytreated regions or those close to adjacent risk zones. We report on our initial experience with tenpatients throughout bite-block fabrication, imaging, planning and treatment. We consider the impactof body habitus and location of the target on patient selection.Our initial experience with this technology has taught us valuable lessons for using the Extend System.We have developed procedural tips to aide in its success. Appropriate fabrication of positioning aidsand a comfortable patient are keys to reproducible patient set-up and treatment. Bite-block fabricationincludes a dental impression that is formed to the patient’s mouth. A plug is appropriatelydepressed into the impression material establishing the necessary opening for firm suction to the hardpallet. A vacuum pillow molds to the posterior head and neck. A mark placed at the top of the moldhelps to insert the patient’s head properly for each treatment. A measurement from the arch of thebite-block assembly to the patent’s anterior neck or chest records the height for future setting of thetreatment couch and CT couch during stereotactic imaging. Suction is then applied requiring propertechnique in order to maintain the suction level necessary for patient immobilization. Once the requiredsuction level is reached, the repositioning tool is used to record depth measurements on four sidesof the skull for the CT simulation process. These values provide guidance for duplication of set-up foreach subsequent treatment.Similar to treatment planning for the G-frame, a team of certified Gamma Knife users are required.The site, dose distribution and fractionation pattern are established by this team. Those patientsappropriate for the Extend System are usually given treatments of 3 to 5 fractions over the courseof 2 weeks.This innovative technology has proven successful for multiple patients at our institution in the hypofractionatedtreatment of gliobastoma multiforme, meningioma, leiomyosarcoma, skull base metastases,and brain stem lesions.56

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaPH -106Application of gamma evaluation method inGamma Knife film dosimetry3Hyun-Tai Chung, 1,2 Jeong-Hoon Park, 1 Jung Ho Han, 1,3 Chae-Yong Kim, 1,3 Chang Wan Oh,4Dohee Lee, 2 Tae-Suk Suh, 3 Dong Gyu Kim1Department of Neurosurgery, Seoul National University Bundang Hospital, Korea2Department of Biomedical Engineering, Catholic University of Korea, Seoul, Korea3Department of Neurosurgery, Seoul National University College of Medicine, Korea4Department of Neurosurgery, Asan Medical Center, Seoul, KoreaObjective: Gamma Knife (GK) radiosurgery is a minimally invasive surgical technique for the treatmentof intracranial lesions. It requires sub-millimeter accuracy to minimize neurologic deficits. In thispaper, the delivery accuracy of GK radiosurgery was assessed using gamma evaluation method forplanning dose distribution and film measurement data.Methods: With GK Perfexion (PFX) treatment planning system (TPS), single 4mm, 8mm, 16mm andcomposite shot plans were developed for evaluation. Their planning dose distributions were exportedas DICOM RT files using new function of GK TPS. Maximum dose of 8 Gy was prescribed for fourtest plans. They were irradiated to spherical solid water phantom with GafChromic EBT2 films inaxial and coronal plane. The exposed films were converted to absolute dose by 4th-order polynomialcalibration curve determined with ten calibration films. The film measurement results and planningdose distributions were registered in same Leksell coordinate using in-house software for furtheranalysis. The gamma evaluation method was applied to two dose distributions with various spatialtolerance of 0.3~2.0mm and dosimetric tolerance of 0.3~2.0% to verify the accuracy of GK radiosurgeryinversely. The result of gamma evaluation was assessed with pass rate, dose gamma indexhistogram (DGH) and dose pass rate histogram (DPH).Results: The 20, 50, 80% isodose lines found in film measurement showed close agreement withplanning isodose lines for all dose levels. The comparison of diagonal line profiles across axial planegave similar results. The gamma evaluation method resulted in high pass rates more than 95% within50% isodose line for 0.5mm/0.5% tolerance criteria in both axial and coronal planes. They satisfied1.0mm/1.0% criteria within 20% isodose line. Our DGH and DPH also showed low isodose lineshave inferior gamma indexes and pass rates than higher ones.Conclusions: It was possible to apply gamma evaluation method to GK radiosurgery. For all testplans, planning dose distribution and film measurement met the tolerance criteria of 0.5mm/0.5%within 50% isodose line being used for marginal dose prescription.57

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaPH-154An audit of repositioning accuracy of Extend inthe first year after installation with hints on how tominimize repositioning problems.Michael Torrens, Chryssa Paraskevopoulou, Evangelia KelesidouHygeia Hospital, Athens, GreeceObjective: To analyze the repositioning accuracy of Extend and identify factors that assist in theavoidance of problems and error during repositioning.Methods:Information was gathered prospectively on 14 treatments by Gamma Knife Perfexion usingExtend from 2010-2011. A total number of 398 repositioning check measurements (RCM) wereanalyzed to determine the average error per patient treatment, the average total error, the differencebetween set up and treatment measurements and the possible influence of a learning curve. The repositioningchecks were analyzed in groups according to the direction of the probe – superior (z axis),right or left lateral (x axis) or anterior (y axis). Notes were made at each treatment and problemsrecorded. Statistical analyses included repeated measures Anova and the Friedman test. All measurementsare in mm.Results: The distribution of measurements was not Gaussian. There was a difference in repositioningerror between the setup/CT RCM (mean 0.94±1.20SD, median 0.50) and the CT/treatment RCM(0.67±1.01SD, 0.30) which was significant (P=0.004). Following this observation the setup/CT RCMwere excluded from the total analysis. The average reposition error in each treatment was 0.76, range0.1-2.8, but excluding the one outlier where there was evidently a mistake reduced this to an averageof 0.60±0.45SD with a highest value of 1.5. In the assessment of the variations between the directionof check measurements it was found that anterior (y axis) was most accurate (mean 0.519), right/left(x axis) was intermediate (mean 0.675) and superior (z axis) least accurate (mean 0.891). This trendwas not significant on a Friedman test (P=0.748). There was strong correlation between the repositioningaccuracy and the time elapsed after installation (P

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaPH-160A simple proposal to reduce cervical target movementduring Leksell Perfexion® Gamma Knife radiosurgeryL Dade Lunsford, Daniel Tonetti, Jagdish BhatnagarUniversity of PittsburghObjective: The design of the Leksell Perfexion ® (PFX) Gamma Knife facilitates inferior target stereotacticradiosurgery (SRS) providing that the target itself is above the standard G-frame base ring.Concern has been raised about the potential of target movement in the region from the occiput to C4.This study documents the potential target deviation using the current Leksell frame.Methods: A commercially available skull and cervical spine model was adapted for SRS using theLeksell PFX Gamma Knife. Both CT and fluoroscopic imaging were performed to determine thepotential for target deviations at standard Gamma Knife angles of 70, 90, and 110 degrees. In addition,target deviation at various heights of the patient positioning table was compared to a standard90 degree angle.Results: Multiple radio-opaque targets embedded in the model showed target deviations which rangedfrom as low as 0.58mm at the medial C1-occiput junction to 13.32mm at C3-4 during 70° extension.Target deviation relative to a 90° CT scan at 110° flexion showed deviations that ranged from2.79mm at the C1-occiput junction to 17.53mm for the medial target at the C3-4 junction.Relative to a PFX shoulder table height of 4.5cm, target deviation at a height of 3cm varied from0.436mm to 5.255mm. For a height at 5.5cm, target deviation varied from 0.436mm to 3.598mm.For a height at a maximum of 5.8cm, target deviation varied from 0.617mm to 4.298mm.Using the standard G frame, placed as inferiorly on the head as possible using ear bar extenders, wecan reliably image to C4 using MRI and CT co-registration. A commercially available cervico-thoracicMRI compatible brace placed before frame application will significantly reduce target deviationrelated to imaging and treatment portions of SRS procedures.Conclusions: As expected, target deviation grossly exceeds clinical tolerance and was determined to begreater the further the distance from the occiput to the cervical spine target. Simple and reproduciblemethods that allow centers to treat inferior targets reliably without the need for reengineering thecurrently widely available G frame may increase the range of targets that can be treated effectivelyusing the current model of the LGK PFX.59

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaPH-191Inter- and intra-fraction performance of the Gamma KnifeExtend System for patient positioning and immobilizationDavid Schlesinger, Chun-Po Yen, Zhiyuan Xu, Jason SheehanUniversity of VirginiaObjective: The Gamma Knife Extend System makes possible multi-fraction Gamma Knife treatments.The Extend System consists of a vacuum-monitored immobilization frame and a positioning measurementsystem to determine the location of the patient’s head within the frame at the time of simulationimaging and before each treatment fraction. The measurement system consists of a RepositioningCheck Tool (RCT) that attaches to the Extend frame, and associated digital measuring gauges. Thepurpose of this study is to evaluate the pre-fraction repositioning and intra-fraction immobilizationperformance of the Extend System for the first ten patients (n=36 fractions) treated at the Universityof Virginia.Methods: For each patient, the RCT was used to acquire a set of reference measurements of thepatient’s position at the time of CT simulation. Before each fraction repositioning measurements wereacquired, and the patient position was adjusted until the residual radial difference from the referenceposition measurements were less than 1mm (if possible). After treatment, position measurements wereacquired and the difference from the pre-fraction position was calculated as a measure of immobilizationcapability.Analysis of patient setup and immobilization performance included calculation of group mean, standarddeviation (SD), and distribution of systematic (components affecting all fractions) and random(per-fraction) uncertainty components.Results: Across all patients and fractions, the achieved mean radial setup difference from the referencemeasurements was 0.65mm, SD=0.24mm. The distribution of systematic uncertainty was 0.17mm.The distribution of random uncertainty was 0.16mm. The RMS differences for each plate wereright=0.35mm; left=0.41mm; superior=0.28mm; anterior=0.20mm.The mean intrafractional positional difference across all treatments was 0.46mm, SD=0.30mm. Thedistribution of systematic uncertainty was 0.19mm. The distribution of random uncertainty was0.22mm. One treatment fraction was excluded from the analysis because the vacuum monitoringinterlock detected patient motion, requiring mid-fraction repositioning.Conclusions: With appropriate patient selection, the Extend system can be used to reposition patientswith sub-millimeter precision, and appears to have adequate immobilization capability. However, careshould be taken to acquire measurements that can implicitly account for rotations of the patient’shead. Further work is required to determine the sensitivity of the vacuum interlock to detect patientmotion.60

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaPH-199Comparison of radiosurgical treatment parameters betweenthe Perfexion and previous Gamma Knife modelYong-Seok Im, Kwang-Mook Park, Jung-Il LeeDepartment of Neurosurgery, Samsung Medical Center, Seoul, KoreaObjective: We compared radiosurgical treatment parameters between the Leksell Gamma Knife(LGK)Perfexion(PFX) and previous models(LGK B/C).Methods: At our center, 495 patients were treated with the LGK B(Jan. 2002 – Feb. 2004). 3,102patients were treated with the LGK C(Mar. 2004 – May 2010). 803 patients were treated with thePFX(Jun. 2010 – Jul. 2011). Treatment parameters were evaluated and compared by measuring thegradient index(GI), conformity index(CI), Paddick conformity index(PCI), selectivity index(SI), beamon time(BT), treatment time, treatment position type, and collision risk.Analysis of patient setup and immobilization performance included calculation of group mean,standard deviation (SD), and distribution of systematic (components affecting all fractions) andrandom (per-fraction) uncertainty components.Results: In the similar dose rate (range 3.1~3.4Gy/min), the median total time in the treatmentroom per patient was 56min (BT=53min) for PFX, 77min (BT=40min) for LGK C(C), and 96min(BT=35min) for LGK B(B). In the whole population, The collision check was predicted byGammaPlan for at least one shot in 5.4% of the patients treated with PFX and in 58.8% of thepatients treated with C. The collision risk requiring technical adjustment(lateral position mode) wasobserved in 4.9% of the patients treated with C, and 2.4% of the patients treated with B. Technicalfailures for at least one shot occurred in 0.4% of the patients with PFX, 1.0% of the patients with C,and 1.0% of the patients with B. In vestibular schwannoma, the median values of GI in PFX, C andB were 2.65, 2.75 and 2.68, respectively. The CI in PFX, C and B were 1.17, 1.32 and 1.25. The PCIin PFX, C and B were 0.79, 0.73 and 0.76. The SI in PFX, C and B were 0.83, 0.75 and 0.78. Thecoverage and conformity indices were similar with both units.Conclusions: LGK PFX proved a high efficiency in treatment delivery by comparison with previousmodels. The clinical setting time and the QA procedure were reduced by the PFX.61

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaPH-200International Leksell Gamma Knife Calibration Survey– Final Results1,3Josef Novotny Jr., 2 Marc Desrosiers, 1 Jagdish Bhatnagar, 3 Josef Novotny, 4 Masaaki Yamamoto,1Saiful Huq, 2 James Puhl, 5 Dade Lunsford1Department of Radiation Oncology, University of Pittsburgh Cancer Institute, Pit2National Institute of Standards and Technology, US Department of Commerce, Gaith3Department of Medical Physics, Na Homolce Hospital, Prague, Czech Republic4Katsuta Hospital Mito Gamma House, Hitachinaka, Japan5Department of Neurological Surgery, University of Pittsburgh Medical Center, PitObjective: Survey approximately 100 Leksell Gamma Knife (LGK) units worldwide to 1) gather detailedinformation about calibration procedures and to 2) measure output of the surveyed LGK units.Methods: Each participant of the project received a LGK calibration questionnaire seeking thefollowing information: LGK model, calibration protocol, phantom, and ion chamber used for calibration,LGK calibration personnel, whether independent verification of calibration was performed, andrelative collimator output factors used. Alanine dosimeters were used to measure the dose rate of eachsurveyed LGK unit and these results compared with calibration data.Results: To date, 70 LGK units from 66 different centers spanning 15 different countries haveparticipated in this study (35 North America, 13 Europe, 21 Asia and 1 South America). Thecalibration protocols used are: AAPM TG21 (26), AAPM TG51 (7), IAEA TRS277 (1), IAEATRS398 (29), NPL Code of Practice (5) and DIN 6800-2 (2). ELEKTA ABS phantom was used in 65(93%) and ELEKTA solid water phantom in 5 (7%) units. Ion chambers most frequently used forthe calibration are: PTW 31010 (0.125 cm3) 26 times (37%), Exradin A16 (0.007 cm3) 12 times(17%) and Capintec PR-05P (0.070 cm3) 11 times (16%). Calibration of the LGK was performed byan on-site physicist in 52 (75%) cases, by ELEKTA physicist in 17 (24%) cases and in 1 (1%) casecalibration was done by a consulting physicist. Independent verification was done only in 31 (44%)cases; RPC, IAEA or similar audit was done only in 20 (29%) cases. All LGK units surveyed arecurrently using the default values for collimator relative output factors. Observed deviations betweenLGK users reported calibration and alanine dosimetry measurements were of small magnitude withmean value of 1.6%. In total 63 (90%) LGK units were within 3% deviation. None of measured unitsexceeded 4% deviation in calibration.Conclusions: Different calibration procedures, especially calibration protocols are used worldwide.Small but systematic deviation between LGK users reported calibration and alanine dosimetrymeasurements are observed for LGK centers in Europe and Asia where IAEA TRS398 protocolis used. This can be explained by the fact that the ABS plastic phantom is considered to be waterequivalent.62

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaPH-236Improvement of the total clinical accuracy ofgamma knife radiosurgery and assessment of theclinical impact of MR spatial distortions2Michael Torrens, 1,2 Pantelis Karaisko, 1 Argyris Moutsatos, 3 Ioannis Seimenis,1Panagiotis Papagiannis, 1 Evangelos Georgiou, 2 Christos Stergiou1Medical Physics Department, Medical School, University of Athens, Greece2Gamma Knife Department, Hygeia Hospital, Athens, Greece3Medical Physics Department, Medical School, University of Thrace, GreeceObjective: The total clinical accuracy of GK treatment delivery may be impaired due to the spatialdistortion inherent in the MR images used for target volume definition in 3D space. This work presentsa time-efficient method to improve the total clinical accuracy of GK radiosurgery by correcting theMR images for background field distortions which, as we have published previously, are a majorcontributor to accuracy degradation (~1mm).Methods: The proposed method is based on the acquisition of an extra MR sequence that adds onlyminutes to the total patient scan-time and an appropriate software tool written in Matlab to processthe “corrected” MR series. The method was benchmarked at 1.5 T using phantoms and then usedto assess the effect of the sequence–dependent spatial distortions in 12 patient treatments with a totalnumber of 80 relatively small metastases (less than 2cm in diameter, with 88 % of them less than1cm and 55% less than 0.5cm). Using the extra MR sequence acquired for all patients, a “corrected”MR series was produced in one-to-one correspondence for every “original” Gd-enhanced T1W seriesroutinely used for target definition. Then the targets corresponding to the different metastases werecontoured on both the “original” and “corrected” series. Patient plans based on the “original” MRseries were finally produced.Results: The prescription dose was 25 Gy and the target coverage more than 99% for all targetscontoured in the “original” MR images. For the same plans, the 25Gy target coverage was found tobe less than 93% for 41% of the targets contoured in the “corrected” MR images (54% of the targetswith diameter 1cm). For thesetargets, a dose of less than 23Gy (18–23Gy) instead of the prescribed 25Gy covered the 99% of thetarget volume (dose difference >8%).Conclusions: There is a fundamental inaccuracy induced by background field spatial distortions onMRI. Small targets especially may be incorrectly covered by routine planning methods. The proposedmethodology was found to minimize the distortions and thus to improve significantly (in sub-voxeldimensions) the total clinical accuracy.63

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaPH-242Initial performance characterization and clinicalimplementation of a novel image-guided system for Perfexion1,2Mark Ruschin, 1 Paul De Jean, 1 Steve Ansell, 1 Greg Bootsma, 1,2 Caroline Chung, 1,2 Cynthia Menard,1,2Young-Bin Cho, 1,2 David Jaffray1Radiation Medicine Program, Princess Margaret Hospital, Toronto, ON, Canada2Department of Radiation Oncology, University of Toronto, Toronto, ON, CanadaObjective: A novel cone-beam CT (CBCT) image-guidance system has been installed on a Perfexionunit at our institution and has been used for patient imaging. The purpose of this study is to describethe initial performance and clinical experience with this image-guided Perfexion (IGP) system.Methods: The initial CBCT prototype could achieve a 188-degree scan. Adjustable imaging parametersincluded: beam quality (tube potential and filter), patient dose, scan speed, reconstructionresolution, and number of projections. The optimal beam quality was determined by measuring thecontrast-to-noise ratio in known objects at different tube potentials and filter combinations. Withthe optimized beam quality, the minimum required patient dose for sufficient image quality was thendetermined by reviewing images of anthropomorphic phantoms. Target localization accuracy wasdetermined by simulating the treatment planning process in end-to-end testing in phantoms usingCBCT images defined in Gammaplan. Our initial clinical protocol was designed to allow CBCTimages of patients with brain metastases to be acquired immediately prior to and after treatment andretrospectively analyzed for setup accuracy and intra-fraction motion.Results: The optimal beam quality – taking into account contrast and patient dose – was determinedto be 90 kV with a bowtie filter plus 0.1mm copper. Using 0.5mAs per projection and 188 projections(1 per degree) resulted in a CBCT dose of approximately 1cGy to the centre of a 16cm head phantom.Low-contrast details such as polyethylene inserts (CT number=-100) in water could be detected. Highcontrast resolution of 7-8lp/cm and 3-4lp/cm was attained using 0.5mm and 1.0mm reconstructedcubic voxels respectively. The scan time was set to 1min, after which the reconstructed volume isavailable in

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaPH-256A treatment planning algorithm optimizing TCP based on adose-rate dependent LQ-modelHåkan Nordström, Karl Danielsson, Pär LidbergElekta Instrument AB Box 7593, SE-10393 StockholmObjective: Planning objectives in the Gamma Knife ® Radio Surgery are in general to have a highcoverage and selectivity of the planning iso-dose to the target as well as low dose to surroundingtissue and organs at risk (OARs). The basic assumption is that there is a strong correlation betweenthe clinical outcome and the physical prescribed dose. As has been pointed out by several authors theradiobiological effect may also be dependent on overall treatment time, a function of both the doseratein tissue and the number of iso-centers used, for which models that have been developed that takethese variables into account. The purpose of this study is to discuss planning based on radiobiologicalmodels rather than physical dosimetric based objectives.Methods: A prototype version of the inverse planning software in Leksell Gamma Plan ® has beendeveloped that optimizes the tumor control probability (TCP) calculated with a modified LQ-modelsuggested by J. Hopewell, B. Millar et al. This model depends explicitly on the dose rate as a functionof time during the treatment delivery. Penalty functions for OARs are also incorporated in the optimization.For several clinical indications TCP-optimized plans have been derived and compared to plansbased on dose metrics (coverage, selectivity and dose gradients). Plans with similar dose metrics butwith different number of iso-centers have been generated to see the influence of dose-rate on TCP.To the test the sensitivity on the outcome the parameter α and β as well as the half-times repair ofsublethal radiation damage have been varied.Results: The suggested method makes it possible to create plans optimized with regards to TCPdetermined by models incorporating dose-rate.TCP optimized plans will in general be different to plans based on optimized dose metrics.Conclusion: A framework has been created that makes it possible to include radiobiological objectivesinto dose plan optimization.65

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaPH-262Variability in target delineation and assessment of theaverage target in stereotactic radiosurgery– a multiobserver study1Helena Sandström, 2 Håkan Nordström, 2 Jonas Johansson, 3 Iuliana Toma-Dasu1Stockholm University2Elekta Instrument AB3Medical Radiation Physics, Stockholm University and Karolinska InstitutetObjective: Four brain disorders of a general complex nature, anaplastic astrocytoma, AVM, meningiomaand vestibular schwannoma were analysed with respect to the variability of target delineation with theaim of determining the average target and the average target coverage for each of them.Methods: Anaplastic astrocytoma, AVM, meningioma and vestibular schwannoma, were chosen becausethey are prone to pose difficulties in delineation. Twenty centres chosen for their high experience withLeksell Gamma Knife ® participated in the study which resulted in a total of 60 treatment plans. Theanalysis of the delineated targets was based on a calculated average target which was compared to eachdelineated target by the concordance index and discordance index to evaluate the coverage of averagetarget to resemble a true target. The difference in target structure location, size and shape was analyzedusing the encompassing volume compared to the common volume of all delineated structures.Results: Target delineation resulted in considerable differences in the planned target volume regardingsize, position and shape. These variations translated into corresponding discrepancies in average targetfor each disorder. The largest difference regarding the indexes between the average target assumedto resemble the accurate target and the planned one was observed for anaplastic astrocytoma witha concordance index of 0.45 (0-0.85) and for vestibular schwannoma with a discordance index of1.13 cm3 (0.16-4.67 cm3).Conclusions: The differences between the targets delineated by various observers for the investigatedfour brain disorders appear to be clinically significant with respect to the average target.66

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaPH-265Quantitative validation of a new semi-automatic inverseplanning software in Leksell GammaPlan ® version 10.1 bycomparison with clinically applied manual dose plans1Tobias Nelder, 1 Thomas Kraepelien, 2 Bodo Lippitz1Department of Medical Physics, Karolinska University Hospital2Gamma Knife Center, Department of Neurosurgery, Karolinska University HospitalObjective: A new automatized dose planning tool Inverse Planning [IP] has been implemented in arecent version of the treatment planning system Leksell GammaPlan ® v.10 for Gamma Knife radiosurgery.The current study aims to quantify performance of the new dose planning tool compared tothe previously used manually optimized dose planning system.Methods: Clinically applied manual dose plans of 50 consecutive patients (63 targets) treated forintracranial metastasis at the Karolinska University Hospital Gamma Knife Center between 2004-07-27to 2005-01-18 were recreated using the new automatized IP system in Leksell GammaPlan ® version10.1 and were quantitatively compared with the manual treatment plans according to a standardizedquantitative criteria. Target coverage, selectivity, gradient index, conformity index and Paddick’sconformity index, together with the KARE-factor was calculated.Results: Each new recreated plan with IP was pairwise compared to their manually planned [MP]counterpart with regard to these parameters. It was shown that a significant improvement in all of theparameters except for target coverage could be achieved. A mean percentage difference introducedwith IP was calculated, selectivity improved with 9.6% (IP: median 0.76: range 0.40-0.90 vs. MP:median 0.69: range 0.32-0.89 (P

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaPH-291TMR 10: A comparison with TMR classic forclinical treatment plans1,2,3,4Ian Paddick, 5 Jonas Johansson1Cromwell Hospital Gamma Knife Centre,, London, UK2London Gamma Knife Centre, Barts Hospital, London, UK3Thornbury Radiosurgery Centre, Sheffield, UK4St. Elisabeth Gamma Knife, Tilburg, Netherlands5Elekta Instrument AB, Stockholm, SwedenObjective: Leksell GammaPlan 10.0 introduced an improved dose calculation algorithm, TMR 10,which entails new beam profiles, depth doses and output factors. This enhanced beam modelling hasmade inaccuracies of the previous algorithm, TMR Classic, apparent. Furthermore, multi-isocentricplanning techniques can amplify subtle differences in single shot profiles, which in turn can affectthe dose calculated, normalisation and beam on time. We aimed to quantify dosimetrical differencesbetween the two algorithms.Methods: 30 targets planned with TMR Classic for the Leksell Gamma Knife ® Perfexion (PFX)were retrospectively re-calculated using the TMR 10 algorithm. This method was repeated for 37targets planned for the Model B/C. The maximum dose, the mean dose to the target, and themaximum dose to the organs at risk (OARs) were compared.In a non-clinical investigation, the greatest dose discrepancy possible between the two algorithmswas also explored.Results: Assuming that TMR 10 correctly calculates dose to the skull, TMR Classic generallyunderestimated maximum Perfexion doses by 2.0% (range: -3.3% to 6.7%), mean doses 1.5%(range: -2.0% to 5.3%) and OARs 3.6% (range: -3.9 to 7.1%).Model B/C data differed by less. TMR Classic underestimated maximum doses by an average of 1.2%(range: -0.7% to 4.2%), mean doses 0.9% (range: -1.3% to 2.7%) and overestimated OARs by 1.8%(range: -0.9% to 4.5%).In a non-clinical setting, the largest discrepancy was for a plan with 8mm and 16mm shots withidentical x and y coordinates, but with the 8mm shot placed 13.0mm in the superior direction. TMRClassic recorded a maximum dose 18.1% lower than that of TMR 10.Conclusion: Dosimetrical differences between the two algorithms can be significant in certain circumstances.Fortunately, dose differences between TMR Classic for Model B/C (where most of our empiricaldata lies) and TMR 10 is minimal. Doses to OARs were typically underestimated by TMR Classic forPFX, but overestimated for the Model B/C. As a result, some users may be unintentionally giving dosesto OARs that are several percent higher with PFX. When quoting doses to critical structures with clinicalresults, users should recalculate the doses delivered using TMR 10.68

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaPH-296Monte Carlo calculated and experimentally verifiedcorrection factors for clinical reference dosimetry forthe Leksell Gamma Knife ® : Application of a new IAEAdosimetry formalism1Jonas Johansson, 1 B. Górka, 2,4 J. Novotny Jr, 3 J.D. Bourland, 2 J. Bhatnagar, 2 G. Bednarz,3R.C.M. Best, 5 L. Persson, 1 H. Nordström, 1 O. Svärm1Elekta Instrument AB, Box 7593, SE-103 93, Stockholm, Sweden2University of Pittsburgh Cancer Institute, Pittsburgh, PA 15213, USA3Wake Forest School of Medicine, Winston-Salem, North Carolina 27157, USA4Na Homolce Hospital, Prague 150 30, Czech Republic5Swedish Radiation Safety Authority, Solna strandväg 96, 171 16 StockholmObjective: Dosimetrical measurements for the Leksell Gamma Knife® (LGK) are challenging due tothe possible lack of electronic equilibrium, spectral changes with field size, and partial occlusion ofthe primary source. The IAEA working group on reference dosimetry of small and nonstandard fieldshave published a new dosimetry formalism. The objective of this work is to report Monte Carlo (MC)calculated and experimentally verified correction factors for a number of ionization chambers that areneeded for the application of the new IAEA formalism to LGK dosimetry.Methods: According to the new IAEA formalism, the absorbed dose to water is given byThis formalism links the standard reference field (f ref) used at a SSDL and the machine specific referencefield (f msr), used in the clinic, via the correction factor . Correction factors for eight differentsmall volume ionization chamber types (0.007-0.125 cm3) from various manufacturers used for LGKdosimetry were determined using MC simulations. Verification of MC simulated correction factorswere done at three LGK facilities and the Swedish SSDL through an international collaboration.Measurements followed a prescribed procedure to provide consistency and accuracy in the acquireddatasets. The absorbed dose to water was determined using IAEA TRS-398 and the new IAEA smallfield formalism.Results: Applying the correction factor using the new formalism leads to, depending on the ionizationchamber and phantom configuration, an increase in the dose-rate between 0.8%-1.6% for PFX and0.3%-0.5% for LGKC compared to IAEA TRS-398. The average standard deviation in the dose-ratemeasurement decreases from about 1% applying TRS-398 to about 0.6% applying the new formalism.Conclusion: With the new formalism, average dose rate is higher and the standard deviation isdecreased slightly compared to IAEA TRS-398. This suggests that small improvements in the accuracyof Gamma Knife ® dosimetry can be accomplished through the implementation of the new formalismusing the correction factors reported in this study.69

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaVA-39Hypertension may not convey excess risk ofradiation-induced change in Gamma Knife radiosurgery ofcerebral arteriovenous malformation1Mark Quigg, 2 Chun-Po Yen, 1 Micaela Chatman, 1 Anders Quigg, 2 Jason Sheehan1University of Virginia, Dept of Neurology2University of Virginia, Dept of NeurosurgeryObjective: No studies exist to determine the excess risk of radiation toxicity in patients with diabetesmellitus or hypertension who undergo Gamma Knife radiosurgery (RS) of cerebral arteriovenousmalformation (AVM). Limited studies suggest DM and HTN are associated with excessive complicationsfollowing fractionated radiotherapy of lesions outside the central nervous system.Methods: This single-center, retrospective, consecutive case series determined the associations betweenradiation-induced changes (RIC) visible on MRI following RS for AVM. Patients with incompletefollow-up and children ≤ 17 years were excluded. History or medication use for DM or HTN, tobaccouse, age, sex, AVM volume, Spetzler-Martin severity grade (1-2 vs 3-5), pre-RS surgery, embolization,or hemorrhage were compared between RIC(+) and RIC(–) groups by univariate and logistic regressionmultivariate analyses.Results: RIC occurred in 38% of 539 adults within 12±10 months (mean±standard deviation) of RSin a median follow-up of 55 months. 34% of those with RIC had symptoms of headache, neurologicaldeficits, or new-onset seizures, with larger RIC associated with greater symptomatology. DM (3% ofsample) was significantly higher with RIC (RIC(+) 5%, RIC(–) 1%, P=0.02 Fisher’s exact test), butHTN (20%) was not. Larger AVM volume and Spetzler-Martin grades 3-5 had significant associationswith RIC. The proportion of patients with pre-RS surgery and pre-RS hemorrhage were significantlydecreased in the RIC(+) group. Older age had borderline associations with RIC. Sex, tobacco use, orpre-RS AVM embolization had no associations with RIC. The factors significantly associated withRIC in multivariate analysis were larger AVM volumes, Spetzler-Martin grades 3-5, and absence ofpre-RS surgery.Conclusions: HTN, traditionally considered to increase the risk of RS in the CNS, did not carrysignificant risks in development of RIC. The number of patients with DM was too low to determinerisk accurately.70

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaVA-50Treatment results of radiosurgery for cerebralarteriovenous malformations in the modern APS eraShunsuke Kawamoto, Fumi Higuchi, Phyo KimDepartment of Neurosurgery, Dokkyo University School of MedicineObjective: The authors sought to assess the efficacy and safety of gamma knife radiosurgery (GKRS)with meticulously-planned conformal coverage using multiple small isocenters in 47 patients withcerebral arteriovenous malformations (AVMs) treated by GammaKnife Type C between 2005 and2008.Methods: The mean volume of AVMs was 4.3 ml (range, 0.04-27.4). Eight patients had AVM niduslarger than 10ml. Dose planning was primarily based on MR angiography and was confirmed ondigital subtraction angiography (DSA). The mean marginal dose was 21.3 Gy (range, 16.7-25). Totalnumber of isocenters used in irradiation ranged from 2 to 76 (mean 27, median 27). In the follow-upperiod, MR images were taken every six months, and DSA was performed to confirm nidus obliterationat 3 years or earlier after GKRS. Outcomes such as the rates of obliteration, hemorrhage after treatment,and adverse radiation effects were analysed.Results: All the 46 patients were followed up for longer than 3 years. Thirty-seven of them underwentDSA and thirty-five (94.6%) showed complete obliteration. In Kaplan-Meier analysis, the completeobliteration rate at 36 months was 97.8% for AVMs with a volume of less than 10 ml. The margindose was the single factor associated with higher obliteration rate (p=0.022). Moderate to extensiveradiation-induced edema was revealed on MR images in 21.3% (10 of 47). The number of totalisocenters was the single significant factor associated with development of radiation-induced edema(p=0.03). Ten of 47 (21.3%) developed new or worsened neurologic symptom and three (6.4%)persisted. Six patients (12.8%) suffered hemorrhage from their AVMs after GKRS; two died of thehemorrhage and one became severely disabled. Among the eight patients with AVMs larger than 10ml, five (62.5%) suffered hemorrhage.Conclusions: Meticulous conformal coverage using multiple small isocenters contributed to higherobliteration rates at earlier stage after GKRS than previously reported, but does not lead to decreasein complication, and might be associated with higher bleeding rate with larger AVMs during thelatency period.71

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaVA-56Gamma Knife Surgery for the Management of IntrinsicBrainstem Tumors and Vascular LesionsDavid Hung-Chi PanTaipei Veterans General HospitalObjective: We present a retrospective study of 111 patients with intrinsic brainstem lesions treated byGamma Knife surgery (GKS) between 1993-2009.Methods: These lesions include 26 gliomas, 49 cavernous malformations, 20 AVMs and 16 metastatictumors. Criteria of patients’ selection for GKS are based on thorough clinical and imaging studies toshow a well-demarcated lesion in the brain stem which is difficult to treat with conventional surgeryor radiotherapy. During GKS, varied radiosurgical doses to the lesion margin were prescribed basedon the lesion size and nature: AVMs 15-22Gy, gliomas and cavernous malformations 10.5-12Gy, andmetastasis 11.5-20Gy. After radiosurgery, all patients underwent regular imaging follow-ups every2-6 months to assess treatment results. For AVMs, a final angiogram was performed 2-4 years posttreatmentto verify complete obliteration.Results: In 20 AVMs, 15 have shown angiographically confirmed complete obliteration. The obliterationrate was 75%. Complications included 1 (5%) radiation-induced edema, 1 (5%) mild rebleeding and2 (10%) focal infarction with hemiparesis. There was no mortality. In 49 cavernous malformations,the annual hemorrhagic rate significantly reduced from 28.2% of the pre-GKS status to 3.33% within2 years post-GKS, and further reduced to 1.74% over 2 years after radiosurgery. In 26 gliomas, thefollow-up time ranged from 6-181 months (median 37 months). Post-GKS MRI revealed tumorregression in 8 (30%), stable in 9 (35%), and enlarged in 9 (35%). Five (19%) glioma patients dieddue to tumor progression, others (81%) were clinically stable after GKS. In 16 patients with metastatictumors, a prolonged survival over 12 months with initial shrinkage of tumors was observed in 10patients.Conclusions: Our data suggest that GKS is effective for the treatment of selected brainstem neoplasm orvascular lesions with acceptably low risks. Careful selection of patients before treatment is necessary.72

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaVA-69Long-Term Follow-Up Results of Two-Stage Gamma KnifeRadiosurgery with a ≥3 Year Interval for >10 ccArteriovenous Malformations1Masaaki Tamamoto , 2 Atsuya Akabane, 3 Yuji Matsumaru,1Bierta E. Barfod, 4 Hidetoshi Kasuya, 1 Yoichi Urakawa1Katsuta Hospital Mito GammaHouse2Departments of Neurosurgery, Kanto Medical Center NTT EC3Departments of Neurosurgery, Toranomon Hospital4Departments of Neurosurgery,Tokyo Womenâ€s Medical University Medical Center EastObjective: Little information is available on staged gamma knife radiosurgery (GKRS) with an intervalof ≥3 years for relatively large arteriovenous malformations (AVMs).Methods: Among our 250 AVM patients treated with GKRS during a 16-year period (1988-2004),the courses of 31 (15 females, 16 males, mean age; 29 [range; 10-63] years) were selected for study.The median nidus volume was 14.0 (maximum; 55.8) cc, respectively. In all 31 patients, relatively lowdoses (12-16 Gy at the lesion periphery) were intentionally employed for the first GKRS. The secondGKRS was scheduled for at least 36 months later.Results: Complete nidus obliteration was attained after the first GKRS in one patient. To date, 26patients have undergone a second procedure with a post-GKRS mean interval of 41 (range 24 to 83)months, while two patients refused the second GKRS and no further treatment was not applicablebecause of severely morbid and death due to bleeding in one each. Among the 26 patients, threerefused follow-up DSA, two died due to bleeding and follow-up DSA is awaited in one. The remaining20 paients have undergone follow-up DSA. Complete nidus obliteration was confirmed in 13 (65.0%),remarkable shrinkage in the other seven (35.0%). In the two of the seven patients, a third GKRSachieved complete nidus obliteration. Therefore, the cumulative complete obliteration rate in thisseries was 76.2% (16[1+13+2]/21 eligible patients). Seven patients (22.6%) experienced bleeding; sixbefore and one after GKRS. Mild symptomatic GKRS-related complications occurred in two patients(6.5%).Conclusions: Although a final conclusion awaits further studies and patient follow-up, these resultssuggest two-stage GKRS to have certain benefits even for relatively large AVMs.73

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaVA-77Mechanism of cyst formation and enlargement followinggamma knife surgery for arteriovenous malformationTakashi Shuto, Shigeo Matsunaga, Makoto OhtakeYokohama Rosai HospitalObjective: This study retrospectively analyzed the clinical characteristics of patients who presentedwith cyst formation following gamma knife surgery (GKS) for arteriovenous malformation (AVM),and mainly discusses the mechanism of cyst enlargement.Methods: Twelve male and five female patients aged 17 to 47 years (mean 28.7 years) were retrospectivelyidentified among 750 patients who underwent GKS for AVM at our institution. The calculatednidus volume, prescription dose to the nidus margin, timing of occurrence of neuroimaging change,follow-up imaging of cysts, findings during surgery, and pathological findings of the cyst wall andassociated granulomatous lesions were investigated.Results: Expanding hematoma was associated with cyst formation in 4 patients. The mean nidusvolume at the time of GKS was 10.1 ml (0.1-26.7 ml), and the mean prescription dose at the nidusmargin was 20.3 Gy (18-28 Gy). Complete obliteration of nidus was obtained in 12 patients, partialobliteration in 4, and no change in 1. Cyst formation was detected at 2.6-15 years (mean 6.9 years)after GKS. Two patients underwent craniotomy for cyst opening and removal of the incompletelyobliterated nidus, and two received placement of Ommaya reservoir. Spontaneous regression of thecyst was observed in one patient. Serial magnetic resonance (MR) imaging was performed in the other15 patients because the cyst showed unchanged size or remained asymptomatic. Histological examinationof cyst wall revealed linear deposits of hemosiderin with gliosis, but no evidence of fresh bleedingin the cyst wall. Histological examination of the enhanced lesion on MR imaging demonstrateddegenerated nidus with infiltration of inflammatory cells and old hemorrhage, and granulation tissuewith chronic hemorrhage from the newly developed capillary vessels.Conclusions: Cysts developing after GKS for AVM enlarge mainly due to repeated minor bleedingfrom angiomatous lesions developing within the degenerated nidus or adjacent brain. The optimaltreatment for such cysts is wide opening with removal of the angiomatous lesion through craniotomy.74

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaVA-107Radiosurgery for unruptured cerebral AVMs: focused onlong-term seizure outcome2Dong Gyu Kim, 1 Seung-Yeob Yang, 2 Hyun-Tai Chung1Department of Neurosurgery, Dongguk University Graduate School, Seoul, Korea2Department of Neurosurgery, Seoul National University College of Medicien, KoreaObjective: To date, seizures in relation to arteriovenous malformations (AVM) have been a secondarytarget of most studies. The insufficient evaluation, in conjunction with the lack of consistent seizureoutcome assessment, has made it been difficult to draw conclusions about seizure outcome afterradiosurgery for AVM. This study aimed to determine the effect of radiosurgery on seizure outcomedepending on AVM obliteration and on the development of new seizure in patients with AVM.Methods: Between 1997 and 2006, 161 consecutive patients underwent radiosurgery for unrupturedAVM and were retrospectively assessed with a mean follow up of 89.8 months by their medicalrecords, updated clinical information and, when necessary, direct patient contact. Seizure outcomewas assessed using the Engel seizure frequency scoring system.Results: Of the 86 patients with a history of seizure before radiosurgery, 76.7% (66/86) were seizurefreeand 58.1% (50/86) were medication-free at the last follow-up visit. Of the patients who achievedAVM obliteration, 96.7% (58/60) were seizure-free while 30.8% (8/26) of those patients who did notachieve AVM obliteration were seizure-free (P=0.001). The proportion of patients who were medication-freewas 81.7% (49/60) of the patients with obliteration and 3.8% (1/26) of patients withoutobliteration (P

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaVA-116Our treatment strategy of cerebralarteriovenous malformation: safer radiosurgerycombined endovascular surgery1Osamu Nagano, 2 Toru Serizawa, 3 Shushi Kominami, 4 Yoshinori Higuchi, 1 Shinji Matsuda,1Kyoko Aoyagi, 5 Toshio Machida, 3 Shiro Kobayashi, 5 Junichi Ono, 4 Naokatsu Saeki1Gamma Knife House, Chiba Cardiovascular Center, Ichihara, Japan2Tokyo Gamma Unit Center, Tsukiji Neurological Clinic, Tokyo, Japan3Department of Neurosurgery, Chiba-Hokuso Hospital, Nippon Medical School, Chiba,4Department of Neurological Surgery, Chiba University, Chiba, Japan5Department of Neurosurgery, Chiba Cardiovascular Center, Ichihara, JapanObjective: We analyzed to define the benefits and risks of gamma knife radiosurgery (GKS) forarteriovenous malformation (AVMs) patients who underwent prior embolization.Methods: Between 1999 and 2011, we performed GKS on 300 patients with cerebral AVMs (nidusvolume less than 10.0 cm3); 100 patients underwent embolization prior to GKS (group A), 200patients without embolization (group B). We evaluated obliteration rate, latency interval hemorrhageand symptomatic delayed radiation injury (DRI) compared between 2 groups using Kaplan-Meiermethod. Our treatment policy is that embolization prior to GKS is necessary for large volume AVM(more than 10.0 cm3), high-flow AVM and intranidul aneurysm in order to reduce the risk of AVMbleeding during latency period and DRI.Results: In this study, 126 patients (63%) had at least one prior hemorrhage in group A and 63patients (63%) included in group B. The median target volume was 3.1 cm3 (range 0.05 to 9.2) ingroup A and 1.7 cm3 (range 0.08 to 9.6) in group B. The median peripheral dose was 19 Gy in groupA and 20 Gy in group B. The actuarial obliteration rates on angiography at 4 years were 90% in groupA and 87% in group B (p=0.37). Latency interval hemorrhage developed in 1 case at group A (cumulativerisk was 1.1% at 10 years) and 8 cases at group B (6.9% at 10 years) (p=0.24). Symptomatic DRIwas observed 2 cases in group A (cumulative risk was 7.0% at 10 years), 7 cases in group B (4.2% at10 years) (p=0.89).Conclusions: Our study demonstrated that prior embolization did not change the obliteration ratewhile it may reduce the risk of AVM bleeding and DRI after GKS.76

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaVA-119Gamma Knife Radiosurgery for dural Arterious venousFistula –the Vienna experienceBrigitte Gatterbauer, Harald Standhardt, Adolf Ertl, Josa Frischer, Engelbert Knosp, Klaus KitzDepartment of Neurosurgery, Medical University Vienna, Währinger Gürtel 18-20, 1Objective: Treatment strategies of dural arterio-venous fistula (dAVF) are diverse including embolisation,surgery, stereotactic radiosurgery and their combination. Spontaneous cure or regression ofsymptoms are reported but a therapeutic approach is warranted in patients presenting with retrogradecortical venous drainage, hemorrhage or aggressive neurological course.The aim of our study is to present GKN as a safe treatment possibility for dAVF.Methods: In a retrospective study we analysed patients presenting with dAVF and treated with GammaKnife radiosurgery (GKN) in our department between 2001 and 2011. 32 patients underwent 40 GKNprocedures. Patients presented different dAVF location most of them cavernous sinus (n=11) andtransverse sinus (n=7). The mean age of patients was 60,3 years (14,7 years SD). Detailed clinicalchart review was performed for all patients.The current clinical status of the patients was assessedvia a neurological examination, resulting in a mean follow up time of 3,3 years (2,2 years SD). Thepatient’s outcome was rated according to their residual symptoms. Descriptive statistical analysisincluded mean values and standard deviation (SD).Results: All patients presented with a broad spectrum of symptoms. In detail intracranial haemorrhage(5), ciliary injection (n=8), exophthalmia (n=9), chemosis (n=8), diplopia (n=6), headache (n=8),visual symptoms (n=7), tinnitus (n=7), elevated intraocular pressure (n=6) vertigo (n=2), ataxia (n=2),dysaesthesia (n=4). 16 patients underwent endovascular embolisation before and one after GKN,in six patients embolisation was tried. GKN was performed with 4, 8, 14, and 18mm collimators,respectively. The irradiated mean volume was 3,3 ccm (5,3 ccm SD). The mean prescription radiationdose was 19,1 Gy (1,7 Gy SD) and the central 37,5 Gy (6,6 Gy SD). In 6 patients a second in one athird GKN treatment was necessary.At the time of follow-up, neuroradiological imaging or clinical symptoms were improved substantiallyin 26% and disappeared completely in 73 % of patients.Conclusions: GKN is an effective treatment for dAVF in patients with a low risk of complications.In our series no further haemorrhage occurred, intraocular pressure normalised rapidly.77

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaVA-171Radiosurgery for symptomatic cavernous malformationsLong-term results of our institute and all over Japan1Yoshihisa Kida, 1 Toshinori Hasegawa, 1 Takenori Katoh1Komaki City Hospital2Scientific Committee of Japanese Leksell Gamma Knife SocietyObjective: Long-term results of radiosurgery to cavernous malformations(CMs) are reported, andcompared with the symptomatic cases treated with surgery or followed up conservatively.Methods: There are 152 cases of symptomatic CMs, either by hemorrhage, neurological deficits or byepilepsy, which were treated with gamma knife(A). There are another 13 cases with surgical resection(B), and 33 cases with conservative treatment(C) as symptomatic controls.Results: Majority of lesions in Group (A) are located in eloquent areas like brainstem or basal ganglia,followed by lobar and cerebellar lesions. With the mean maximum and marginal dose of 26.4 and14.9 Gy respectively, 30% of them showed a shrinkage and the others were unchanged in the meanfollow-up of 55.4 months. Hemorrhage rate after radiosurgery are far decreased to 3.2%/year/case,which is almost one tenth of the one during 5 years before gamma knife (31.8%). Hemorrhage rateshowed 8% in the first year, then apparently decreased to less than 5% subsequently and finallyreached near to 0% in the 7th year. Convulsive seizures associated with CM either disappeared ordecreased in almost 70% of patients, who were treated with gamma knife.In cases of surgical resection, they had a similar hemorrhage rate to Group (A). In contrast, thehemorrhage rate in Group (C) was 7.6 %/year/case during 62 months of mean follow-up, which ismore than double than Group A.Conclusions: The purposes of radiosurgery for symptomatic CMs are not totally irradicate the lesions,but to successfully control the symptomatic events. Because of markedly decreased rate of hemorrhagewith acceptable rate of complications, radiosurgery for cavernous malformation is warranted andadvisable, especially for CMs in brainstem and basal ganglia with less than 15Gy at the margins.However, suprotentorial CMs associated with intractable seizures can be treated with surgery, sincethe effects of radiosurgery are not consitent. Moreover, a higher marginal dose more than 18Gy,which may cause adverse effects more often, is required to successfully control seizures.In this report, the results of radiosurgery from many institutes in Japan are collected and comparedwith ours.78

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaVA-190Gamma knife therapy for cavernous hemangiomas ofthe cavernous sinus: clinical outcome of 39 patients.Wei Wang, Peng Li, Haibo RenDepartment of neurosurgery, West China Hospital of Sichuan UniversityObjective: A retrospective study was carried out to evaluate the efficacy and safety of gamma knife(GK) for cavernous hemangiomas of the cavernous sinus (CHCS).Methods: From July 2004 to March 2010, forty-two patients with CHCS underwent gamma knife therapyat West China Hospital of Sichuan University. Among these patients, 38 patients underwent GKas the initial treatment; the other 4 cases had GK treatment after microsurgery. An average prescriptiondose was 13.3Gy (12-15Gy) at 47.9% (40-50%) isodose line. All patients were followed-up byperiodical enhanced MRI scan and physical examination. The improvement of clinical symptoms andtumor control were analyzed.Results: Thirty-nine patients accomplished follow-up with a mean duration of 38.4 months. Completetumor remission (tumor size decreased more than 90%) was observed in 7 patients. Twenty-eightpatients had significant tumor control (tumor size decreased more than 30%). No significant change intumor size was reported in 4 patients. Clinical symptoms were reported including headache (33 cases),facial numbness (19 cases), facial pain (14 cases) and diplopia (6 cases). Significant improvement inheadache, facial numbness, facial pain and diplopia was reported in 27, 11, 11 and 5 patients respectively.No newly developed cranial nerve damages were observed.Conclusions: The preliminary result indicated that GK might be an effective and safe option forCHCS management. Long term follow-up and more cases are needed to investigate the advantageand disadvantage of this management.79

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaVA-192New nidus found adjacent to the target site of AVM treatedwith Gamma Knife radiosurgery – Report of 3 cases1Do Hoon Kwon, 2 Byung Duk Kwun, 3 Jae Seung Ahn, 4 Do Hee Lee, 5 Hyun Jung Kim1Asan Medical Center, College of Medicine, Univ. of Ulsan, Seoul, Korea2Asan Medical Center3Asan Medical Center4Asan Medical Center5Asan Medical CenterObjective: The new nidus was rarely found adjacent to the resecting margin of nidus after surgicalresection of the AVM especially in the young age group. But the new nidus adjacent to the target siteof AVM treated with radiosurgery had not been reported yet. We reported and reviewed our caseexperiences retrospectively.Methods: The authors retrospectively analyzed their experience in 1,000 cases of AVMs treated withGamma Knife surgery during 20 years. Among them, 3 cases of new nidus were found adjacent tothe target site with an incidence rate of 0.3%. No patient had been treated with embolization beforeradiosurgery. All patent had a history of ICH before or after reradiosurgery.Results: First patient was a 9 year old boy who treated with Gamma Knife for left occipital AVM onemonth after ICH. Treated volume was 600 cumm and 25Gy was irradiated to the margin of the nidus.Thirty one months after radiosurgery, the patient had have 2nd radiosurgery for the new nidus whichwas found adjacent to the target site, treated volume was 900 cumm. Second patient was a 9 yearold boy treated with Gamma Knife for the small AVM located in the cerebellar vermis 1 month afterbleeding. Five years after radiosurgery, he had rebleeding and retreated to the same nidus with GammaKnife 2 month after rebleeding. Six years after 2nd treatment, he had a new nidus adjacent to thetarget site and the volume was increased from 400 cumm (2nd treated volume) to 2,800 cumm. Hehad have 3rd radiosurgery for this new nidus. Third patient was a 33 year old man who treated withradiosurgery for the incidentally detected cerebellar AVM, the nidus volume was 1,100 cumm and 20Gy was irradiated to the nidus. Three years after radiosurgery, patient had cerebellar ICH and newnidus was found adjacent to the target site and 2nd radiosurgery was performed, the nidus volumewas 500 cumm.Conclusions: The new nidus might be developed adjacent to the target site in the treatment of AVMwith radiosurgery, but the incidence was very rare.Key words: nidus, AVM, radiosurgery80

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaVA-266Gamma knife radiosurgery for dural arteriovenous fistulas:A meta-analysis of treatment strategy and results in fourdifferent Gamma knife centers1Huai Che Yang, 1 David Hung Chi Pan, 2 Wan Yuo Guo1Department of Neurosurgery, Taipei Veterans General Hospital2Department of Neuroradiology, Taipei Veterans General HospitalObjective: Treatment options for dural arteriovenous fistulas (DAVFs) have expanded with theapplication of Gamma knife radiosurgery (GKS). To assess the role of GKS in treatment of DAVFs,we reviewed our entire DAVF experience and compared with three recent published DAVFs GKStreatment series from different centers.Methods: Between 1993 and 2010, 368 DAVFs underwent GKS in our hospital. In our series, 216patients were Cavernous-carotid fistulas, 97 patients were transverse-sigmoid fistulas and 55 patientshad DAVF in other location. 327 patients (89%) had only Gamma knife treatment and other 41patients (11%) had combined treatment with embolization or surgery. Seventy-five patients (20%)were diagnosed after sustaining an intracranial hemorrhage. We found more than 95% of patientshad neurological symptom improvement during follow-up. Seventy percent of 216 patients withcavernous-carotid fistulas and 59% of patients with non cavernous-carotid fistulas had obliterationconfirmed by imaging.We selected three recent published GKS series from University of Pittsburgh, University of Virginia,and Karolinska University hospital (series at least had 40 patients with more than 3 years follow-uppublished in recent 5 years) for comparison. We compared patients’ selection, treatment strategy, doseplan, treatment results and complication of four different series and try to find out the commonconclusion in current GKS treatment for DAVFs.Conclusions: GKS is a safe and effective treatment modality for intracranial DAVFs. For lowrisk DAVFs with benign clinical presentation, GKS can serve as a primary treatment. Symptomimprovement rate and image proved obliteration rate can be achieved in more than 70% to 90%within 2 years with little adverse events. For high risk DAVFs with extensive retrograde corticalvenous drainage, hemorrhage or severe venous hypertension, treatment combined with embolizationor surgery is suggested.81

16 th International Meeting of the Leksell Gamma Knife ® SocietyMarch 2012, Sydney, AustraliaP-BE-214Endocrinological evaluation of growth hormone-secretingpituitary macroadenoma invading cavernous sinus treatedby aggressive transsphenoidal resection followed by GammaKnife radiosurgery1Jong Hee Chang, 2 Min Cheol Oh, 2 Eun Jik Lee, 1 Sun Ho Kim1Department of Neurosurgery, Yonsei University Health System,2Department of Endocrinology, Yonsei University Health SystemObjective: The authors would like to determine long-term effect of Gamma Knife radiosurgery (GKS)for the treatment of remnant tumor in the cavernous sinus (CS) after operation using transsphenoidalapproach (TSA) of growth hormone (GH)-secreting pituitary macroadenoma.Methods: Seventeen patients who failed to achieve biochemical remission after TSA were followed fora mean period of 70.2 months (range 17-180) after GKS. All patients underwent regular hormonalexamination including serum GH, IGF-1, oral glucose tolerance test, and combined pituitary functiontest (CPFT). Magnetic resonance imaging (MRI) was performed 6 months after GKS and thensubsequent one year interval. All patients had remnant tumor only in the CS and receivedhormone-suppressive medication, sandostatin LAR before or after GKS.Results: There were 13 women and 4 men with a mean age of 41.8 years (range 27-62). Ten patients( 58.8%) achieved hormonal remission with a mean time of 47 month (median 40, range 18-129)after GKS and mean radiation dose to tumor margin was 27.9 Gy (range 14-35). Mean tumor volumedecreased from 5.2 ml (at pre-GKS MRI) to 3.6 ml (at the last follow-up MRI) (p=0.000). Actuarialrate of hormonal remission at 2, 4, and 6 years were 12.5%, 40%, and 64%, respectively. Intergroupcomparison between remission and non-remission group those who had a minimum hormonal followupperiod of 48 months, showed both ‘serum level of GH’ and ‘degree of decreased GH percentile’ at12 months after GKS showed significant difference (p=0.023), (p=0.014), respectively. A new pituitaryhormone deficiency that has significant difference was found only in gonadal axis (p=0.032) based onlast follow-up CPFT. A radiation necrosis was detected in 4 patients.Conclusions: GKS for the remnant tumor only in the CS after maximal resection of sellar andsuprasellar portion of GH-secreting pituitary macroadenomais effective, especially for minimizingnewly developed post-GKS hypopituitarism. However, careful dose planning and long-term follow-upshould be necessary in terms of prevention and effective management of radiation-inducedcomplications.82

Author IndexAAhluwalia Manmeet 49, 50Ahn Jae Seung 80Akabane Astuya 48Akabane Atsuya 73Angelov Lilyana 36, 50Anh Vuong Duong 40Ansell Steve 64Aoyagi Kyoko 76Arai Yoshio 55Azhir Ramin 41BBadinez Leonardo 29Barani Igor 39Barfod Bierta E 45, 46, 47Barfod Bierta E. 33, 34, 73Barneet Gene 49Barnett Gene 36, 50Bednarz G. 69Bergman Kenneth 22, 24Best R.C.M. 69Bhatnagar J. 69Bhatnagar Jagdish 55, 59, 62Bianchi-Marzoli Stefania 18Bittner Nathan 22, 24Blanchard Jocelyn 23Bolognesi Angelo 18, 19Bootsma Greg 64Bossung Christine 56Bourland J.D. 69Bova Francisco 29Bulthuis Vincent 17Burke Bridget 56Busse Reinhard 40CCacciari Nicoletta 53Carron Romain 25Casserly Ryan 41Chang Cheng-Siu 26Chang Jong Hee 82Chao Sam 49, 50Chao Samuel 36Chatman Micaela 70Cheng Brita 42Chen Peter 41Chernov Mikhail 20Chiang Veronica 6, 30, 54Cho Young-Bin 64Chung Caroline 64Chung Hyun-Tai 8, 57, 75Cubelli Marta 53DDanielsson Karl 65Daspit Phil 15De Jean Paul 64Del Vecchio Antonella 18De Ramón Raúl 29Desrosiers Marc 62Dilman Robert 41Dinca Eduard B. 37Donnet Anne 25Driscoll Colin 10Dryzmala Robert 56Duma Christopher 2, 41EEffendi Khale 23Elson Paul 50Ertl Adolf 77FFerrari da Passano Camillo 18Filiput Eric 56Flickinger John 7, 43, 55Fogh Shannon 39Foote Robert 4, 10Franzin Alberto 18, 19Frischer Josa 77Förander Petter 13GGarces Yolanda 4Gatterbauer Brigitte 77Georgiou Evangelos 63Gerszten Peter 7Gioia Lorenzo 19Giugni Enrico 53Górka B. 69Guo Wan Yuo 81HHan Jung Ho 8, 57Hanssens Patrick 17Hasegawa Toshinori 11, 78Hashemi-Sadraei Neda 49, 50Hashimoto Takao 28Hayashi Motohiro 20, 28Higuchi Fumi 38, 71Higuchi Yoshinori 28, 35, 48, 76Hirai Tatsuo 28, 35Hoggard Nigel 16Hori Tomokatsu 28Horstmann Gerhard 40Huang Chuan-Fu 26Huq Saiful 62IIm Yong-Seok 61Inzucchi Silvio 6Ishido Katsuya 52Iyer Aditya 43Izawa Masahiro 20JJaffray David 64Johansson Jonas 66, 68, 69Jokura Hidfumi 14KKano Hideyuki 43, 55Karaisko Pantelis 63Karaiskos Pantelis 9Kasuya Hidetoshi 73Katoh Takenori 11, 7883

Kaufmann Anthony M 2Kawabe Takuya 33, 34, 45, 46, 47Kawagishi Jun 14, 48Kawamoto Shunsuke 38, 71Kelesidou Evangelia 58Kemeny Andras 12, 16Kemeny Andras A. 37Kessels Fons 17Khandanpour Nader 16Kida Yoshihisa 11, 78Kienstra Barb 56Kim Brian 41Kim Chae-Yong 8, 57Kim Dong Gyu 8, 57, 75Kim Hyun Jung 80Kim Mooseong 27Kim Phyo 38, 71Kim Sun Ho 82Kim Young-Hoon 8Kitz Klaus 77Knisely Jonathan 6, 54Knisely J.P.S 30Knosp Engelbert 77Kobayashi Shiro 76Kominami Shushi 76Kondziolka Douglas 2, 43, 55Koyama Toru 28Kraepelien Thomas 67Kwon Do Hoon 80Kwun Byung Duk 80LLarsen Kent 21Leavitt Jacqueline 31Lee Dohee 57Lee Do Hee 80Lee Eun Jik 82Lee Jung-Il 61Lidberg Pär 65Liem Leon 42Link Michael 31Link Michael J 2, 4, 10Li Peng 79Lippitz Bodo 67Liu Wen-Shan 26Lleva Renee 6Lorenzoni José 29Losa Marco 19Lunsford Dade 62Lunsford L Dade 55, 59Lunsford L. Dade 2, 43Lühr Claudio 29MMachida Toshio 76Mackintosh Ralph 41Ma Lijun 39Marko Nicholas 36Mastras Dean 22, 24Mastuda Shinji 35Mathew Maya Mary 51Mathieu David 2, 23Matsuda Shinji 28, 76Matsumaru Yuji 73Matsunaga Shigeo 74McBride Heyoung 2McDermott Michael 39McDonough Michael 22, 24Medone Marzia 18Menard Cynthia 64Mendez Joseph 39Miller Robert 21Mohammadi Alireza M. 36Mortini Pietro 18, 19Motti Enrico D.F. 53Moutsatos Argyris 63Musella Rosario 21NNagano Osamu 35, 76Nagy Gabor 16Nakazaki Kiyoshi 44Nelder Tobias 67Neyman Gennady 36Niranjan Ajay 43, 55Nordström H. 69Nordström Håkan 65, 66Novotny Josef 7, 55, 62Novotny Jr J. 69Novotny Jr. Josef 62OOchiai Taku 28Oh Chang Wan 8, 57Oh Min Cheol 82Ohtake Makoto 74Ohye Chihiro 28Okada Yoshikazu 20Ono Junichi 35, 76PPaddick Ian 68Paek Sun Ha 8Pan David Hung Chi 81Pan David Hung-Chi 72Pan Hung-Chuan 5Papagiannis Panagiotis 63Paraskevopoulou Chryssa 58Park Jeong-Hoon 57Park Kwang-Mook 61Patel Agam 43Peereboom David 49Persson L. 69Pettegrew Lloyd 21Picozzi Piero 18, 19Pittier Ann 22, 24Plunkett Maryann 41Pollock Bruce 4, 10, 31Porter Randall 15Preotiuc-Pietro Daniel 37Puhl James 62QQuader Mubina 7Quercia Sara 53Quigg Anders 70Quigg Mark 7084

RRadatz Matthias 12, 16Radatz Matthias W.R. 37Rades Dirk 40Rahmatullah Gazanfar 49Rampa Federico 53Reed John 56Reeves Alexa 41Régis Jean 25Ren Haibo 79Resseguier Resseguier Noémie 25Rowe Jeremy 12, 16, 37Rundle Paul 37Ruschin Mark 64SSaeki Naokatsu 35, 48, 76Séguin Mario 23Samura Hirofumi 28Sanders Kevin 22, 24Sandström Helena 66Sato Yasunori 48Schlesinger David 32, 60Schoenberger Amanda 56Seimenis Ioannis 63Serizawa Toru 28, 35, 48, 76Sheehan Jason 2, 3, 32, 60, 70Shibazaki Toru 28Shin Peter 22, 24Shuto Takashi 48, 74Simpson Joseph 56Sneed Penny 39Sorum Randy 22, 24Spatola Giorgio 19Stafford Scott 4, 31Standhardt Harald 77Stergiou Christos 9, 63Stevens Glen 49Sugai Kazuyuki 14Suh John 36, 49, 50Suh Tae-Suk 57Sun Ming-Hsi 5Suzuki Satoshi 52Svärm O. 69Syms Mark 15TTakahashi Kou 14Tamamoto Masaaki 33, 34, 73Tamura Manabu 20Tamura Noriko 20Tanaka Shota 2Te Lie Suan 17Toma-Dasu Iuliana 66Tominaga Teiji 14Tonetti Daniel 59Torrens Michael 9, 58, 63Trampeli Alexandra 9Tu Hsien-Tang 26Tuleasca Constantin 25UUeki Keisuke 38Urakawa Yoichi 33, 34, 46, 47, 73Urakawa Yoihi 45VValle Micol 19Van Eck Albertus 40van Overbeeke Koo 17Vasdekis Vasilis 9Ventrella Laura L.E. 53Vogelbaum Michael 36, 49, 50Vortmeyer A 30WWangerid Theresa 13Wang Herbert 22, 24Wang Wei 79Watts Karen 56Weil Robert 36, 49, 50Weisskopf Peter 15Whicker Margaret 6Whitely Brittany 41XXu Zhiyuan 2, 60YYamamoto Masaaki 45, 46, 47,48, 62Yamamoto Msaaki 35Yamanaka Kazuhiro 48Yamashiro Katsumi 28Yang Dar-Yu 5Yang Huai Che 81Yang Seung-Yeob 75Yen Chun-Po 32, 60, 70Yianni John 16, 37Yomo Shoji 20Young A. Byron 2Yu James 54ZZamagni Claudio 53Zárate Adrián 29Zemanek Alyssa 22, 24Zhiyuan Xu 3285