ABSTRACTS OF THE 21st ANNUAL MEETING OF THE ITALIAN ...

Background: Recent analyses suggest that the fractionation
sensitivity of prostate tumors is high and many
hypofractionated protocols are being tested (1). Since the
alpha/beta ratio estimates for prostate cancer are much lower
than the typical values for many other types of tumor (2), we
performed a small randomized trial to compare a
hypofractionated versus a conventional schedule for
radiotherapy in localized prostate carcinoma. We have already
reported the acute toxicity (3). Now our aim is to evaluate late
gastrointestinal (GI) and genitourinary (GU) toxicities in the
two patient groups and to assess the mathematical model
theoretically predicting equivalent fractionations. Patients and
Methods: From September 2008 to July 2009, 40 patients with
cT1-T2N0M0 prostate cancer were randomized to receive
either a conventional or a hypofractionated radiation therapy
with curative intent. Patients were stratified according to stage,
Gleason score and presenting prostate-specific antigen level;
9 patients were at low risk and 31 patients were at
intermediate risk according to Partin classification. The latter
patient group received neoadjuvant hormonal therapy that
started two months before the radiotherapy onset and
continued during radiotherapy. Treatments were delivered
using four to six coplanar 10-18 MV photon beams at a dose
of 72- 78 Gy in 36-39 fractions within 7-8 weeks, or 64.8-70.2
Gy in 24-26 fractions within 5 weeks. Based on standard
linear-quadratic modeling, the hypofractionated protocol was
designed to keep late complications constant in rectal tissues.
GI and GU toxicities were scored according to the
RTOG/EORTC system. Efficacy of radiotherapy, based on
clinical, radiologic and prostate-specific antigen data, was also
evaluated every three months for two years and every six
months subsequently. Results: All patients completed the
whole course of radiotherapy without interruptions. Minimum
follow-up was one and a half years; median follow-up was 25
months. None of the patients experienced grade 3-4 toxicity.
Grade 1 and grade 2 GI and GU toxicities occurred during and
soon after treatment in both groups without significant
differences. In the long term, 35% of patients in the
hypofractionated group and 40% of patients in the control
group reported increased frequency of urination or nocturia
(p>0.5). Their symptoms cannot be scored as G1 because they
did not reach twice the level of the pretreatment habit. Only
one patient in the hypofractionated group presented an actinic
proctitis (p>0.5); moreover, this patient suffered from a preexisting
hemorrhoidal disease. Discussion and Conclusion: No
difference was noted in the chronic complications between
hypofractionated and conventionally fractionated radiotherapy
groups. As regards late rectal side-effects, according to the
linear-quadratic formula in our study design, late toxicity was
already expected to be equivalent in the two treatment groups.
Our study confirms that hypofractionation is a promising
regimen for prostate cancer radiotherapy and that a linearquadratic
formula is a reliable radiobiological model. The
1888
ANTICANCER RESEARCH 31: 1807-1956 (2011)
follow-up period was long enough to conclude that the
hypofractionated schedule was well tolerated in both the short
and long term and the incidence of clinically significant GI
and GU toxicity after conventional and hypofractionated
radiotherapy appeared to be similar. Longer follow-up is
mandatory to evaluate the effectiveness of the two regimens.
Regarding tumor control, assuming a low alpha/beta ratio for
prostate carcinoma, we expect an interesting therapeutic gain.
1 Brenner DJ et al: Direct evidence that prostate tumors show
high sensitivity to fractionation (low α/β ratio), similar to
late-responding normal tissue. Int J Radiat Oncol Biol Phys
52: 6-13, 2002.
2 Dasu A: Is the α/β value for prostate tumors low enough to
be safely used in clinical trials? Clinical Oncol 19: 289-301,
2007.
3 Spagnoletti G et al: Hypofractionated versus conventionally
fractionated radiation therapy for prostate cancer: our first
results. Anticancer Res 30: 1472-1473, 2010.
148
VIRTUAL HDR CYBERKNIFE ® TREATMENT FOR
LOCALIZED PROSTATE CANCER. PRELIMINARY
EXPERIENCE
Antonio Pontoriero1 , Donatella Arpa1 , Carmelo Siragusa2 ,
Federica Midili2 , Isidora Ielo2 , Giuseppina Anastasi3 ,
Carlo Magno3 and Costantino De Renzis1 1A.O.U. Policlinico "G. Martino" Università degli Studi di
Messina, U.O.C. di Radioterapia, Messina, Italy;
2U.O.C. Fisica Sanitaria and 3U.O.C. Urologia, A.O.U.
Policlinico "G. Martino" Messina, Messina, Italy
Aim: The Cyberknife is an imaging-guided device for
delivering high radiation doses to a precisely defined threedimensional
target volume. The Virtual HDR Cyberknife is
indicated for patients with localized cancer prostate (T1-T2b)
with favorable prognosis (Gleason score ≤6, PSA ≤10 ng/ml)
and selected patients with intermediate prognosis (Gleason
score of 7, PSA 10.2-20 ng/ml). The low α/ß ratio for prostate
cancer requires high radiation with an hypofractionated
schedule of dose for tumor control and it has been shown to be
biologically lethal for prostate cancer cells. In this report, we
summarize preliminary experience with planning emulating
HDR brachytherapy dose distribution. Patients and Methods:
At our institution, over a period of 36 months, 11 patients with
a median age of 78 (range 73-86) years and a median Gleason
score of 6 (range 5-7) were submitted to treatment with the
Virtual HDR Cyberknife. The planning target volume (PTV),
defined with MRI and CT imaging, included the prostate and
seminal vesicles, plus 2 mm of expansion for favorable
prognosis or 5 mm for intermediate prognosis in all directions,