Journal 1pages FINAL 34- - National Board Of Examination

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in non functional differentiated cancersof thyroid.EBRT in differentiated cancer ThyroidPost-operative adjuvant EBRT iseffective in differentiated non functionalthyroid cancers However, it is indicatedfor poor prognostic group of thesepatients. Indications for post operativeEBRT could be residual diseasemicroscopic/macroscopic positive,advance age at diagnosis, extrathyroidalinvasion, high grade cancer, retrosternalthyroid extension, high number of lymphnode involvement.Sheline etal in 1966, reported the use ofadjuvant P.O EBRT in thyroid cancersand their study suggested a positive roleof EBRT in controlling the residual orgross disease in differentiated thyroidcancers although the dose of EBRT wassuboptimal 50 Gy, by present standards. 12Tubiana & colleagues also advocatedpost operative EBRT for patients withmicroscopic or macroscopic residualdisease. Since 1956,their practice hasbeen to deliver 50Gy/25Fr/5weeks tothe neck with boost of 5 to 10 Gy toresidual disease with cobalt-60teletherapy. The spinal cord dose limitedto 42 Gy. They observed a 5 yr. survivalrate of 94% (62 of 66) for patients withcomplete surgery and 78% ( 76 of 97 )patients with incomplete surgery. 13Farahate and coworkers evaluated therole of adjuvant EBRT in 238 patientswith differentiated thyroid cancers afterprimary optimal treatment of surgery ,RAI therapy and TSH suppressivetherapy with thyroid hormones. Analysisof 99 patients showed that adjuvantEBRT improves the recurrence freesurvival in patients older than 40 yearswith invasive papillary thyroid cancer andlymph node involvement. 14At Princess Margaret Hospital theprescription of irradiation is 40 Gy givenin 15 fractions in 3 weeks for microscopicdisease. A boost of 10 Gy in 5 fractionsin 1 week delivered to areas of grosstumour 15 .Pre operative EBRT can be used forborderline inoperable differentiatedthyroid cancers to make them operableor should be approached with curativeintent specially in the patients wheresurgery is contraindicated because of comorbidconditions.Inoperable, bulky disease should beapproached with curative intent.Inoperable, papillary thyroid cancertreated with local EBRT has regressedmarkedly or disappeared with patientsurviving as long as 25 years. Thetreatment field shall encompass the entirethyroid tumour, neck and superiormediastinum. A tumour dose of 65-70Gy in 7-8 weeks is recommended. 16The tumour volume for post operativeEBRT should include the thyroid bedwith 2-3 cm. margin around the primaryand draining lymph nodes. Aim of EBRTshould be homogenous dose distributionand with due care of the spinal cordtolerance as it is very close to the skinsurface in the region of thyroid. A directfield with electron beam with 12-16 MeVenergy is preferable, though a multifieldwedge pair set up with cobalt-60 can beother option. The recent techniques of3-D Conformal Radiotherapy (CRT ) andIntensity modulated Radiation therapy (IMRT ) may help in achieving betterresults with minimum possible toxicityand late complications otherwise reportedby conventional EBRT in thesemalignancies.EBRT in medullary cancer ThyroidThe role and effectiveness of EBRT inmedullary ca. thyroid is still controversial,but it can be used in its treatment aspost operative adjuvant for anymicroscopic residual or gross residualdisease. 17,18,19,20,21,22 T heradiosenstivity of this type of thyroidcancer falls between that of differentiatedand anaplastic cancers. Therecommended dose is 60 Gy in 6-7weeks. In in-operable disease, the doserequired might be higher 65-70 Gy andshrinking field may be appropriate todecrease the acute and late complicationsor recent techniques of 3-D CRT orIMRT may be the answer for deliveringhigh precise dose required .The results of treatment of Medullarythyroid carcinomas with EBRT or CCTare disappointing. 23,24 EBRT leads toincreased toxicity and moreover the localrecurrence rate has also not shown anyimprovement. A study reported fromFrance of 59 patients reported localrecurrence within the radiotherapy fieldin 30% of patients 25 . In medullarycarcinoma thyroid , a modified mantlefrom the level of chin to the 4 th Dorsalvertebra and laterally covering the wholeextent of the neck should be used withspecial attention to the radiation dose tospinal cord.EBRT in anaplastic Thyroid cancerIt is one of the most aggressive cancersof thyroid and lacks the ability toconcentrate radioactive I 131 . A distinctpathological type of this variety smallcell anaplastic carcinoma of thyroid(Insular carcinoma) has shown the abilityto concentrate radioactive I 131 .Aggressive local therapy is indicated inall patients who can tolerate it and inwhom it is technically feasible.EBRT has been used in its treatment asprimary modality with or without surgeryand with or without CCT. EBRT hasalso been used with limited success totreat Anaplastic thyroid carcinoma. It isconsidered to be not much sensitive toradiotherapy.One study from London reported 10 of<strong>Journal</strong> of Postgraduate Medical Education, Training & ResearchVol. I, No. I & II65
17 patients with an objective responseto accelerated radiotherapy (3 CR and 7PR) but the toxicity was considerable 26 .In mid 1980’s Kim & Leeper reportedimproved response to a combination ofEBRT and relative low dose doxorubicinas an apparent synergistic agent achievingresponse in 84% of 19 patients but witha median survival of 12 months only. 27Early diagnosis with aggressive surgicaltherapy supplemented by EBRT anddoxorubicin based CCT is the mostappropriate treatment for patients withAnaplastic thyroid cancer.Tallroth and associates have reported theSwedish experience of anaplastic giantcell cancer at the Radiumhemmet usingthree-drug combination of bleomycin, 5-flourouracil & cyclophosphamide withconventional radiation therapy andaccelerated radiotherapy with equivocalresults. 28EBRT in Thyroid LymphomaThe optimal treatment of thyroidlymphoma has evolved with the successof combination chemotherapy used innon-Hodgkin’s Lymphoma. Role ofsurgery in the thyroid lymphoma is justto obtain adequate tissue for diagnosisby large needle or core needles biopsy.The primary treatment should be EBRTplus combination chemotherapy. 29Some people still advocate surgery forthe primary disease plus EBRT especiallyin patients where there is no evidence ofextra-thyroidal disease. 30 Any extensionof the disease by direct extension orlymph node involvement should beconsidered as systemic disease.The dose of EBRT in lymphomas isfrom 30 – 45 Gy over 3 to 4 weeks withCCT.For very bulky disease higher doseor boost radiotherapy can be considered.EBRT in metastatic cancer ThyroidIn advanced disease with metastasis,EBRT has an important and establishedrole for symptom control and achievinggood palliation. EBRT with or withoutRAI and combination chemotherapy hasbeen utilized for the purpose in differentjudicious combinations. A fractionateddose of 30-45 Gy over 2-4 weeks isjustified in view of expected long termsurvival in advanced cancer thyroid. Anaccelerated high dose palliative EBRTcan also be prescribed in individualsituations. Palliative EBRT is used forbone, brain, hepatic and soft tissuemetastases impending pathologicalfractures, neurological complications andin cases of SVCS .EBRT in secondary ThyroidmalignanciesThe incidence of involvement of thyroidgland by secondary metastasis from othersites is fewer than 1% in clinical situationand its incidence in various autopsy basedseries ranges from 2-25% . The mostcommon malignancies, which metastasizeto thyroid gland, are cancer of lung andbreast. Each accounts for about 25% ofthem 31 .Melanoma, renal cell carcinoma andgastrointestinal malignancies account forapproximately 10%. EBRT can be utilizedin some of these patients to palliate thelocal symptoms in individual situation.Future directions in the management ofcancer ThyroidThe recent explosion of knowledgeregarding the molecular and cellularpathogenesis of cancer has led to thedevelopment of range of targetedtherapies and these are being evaluatedin clinical practice of various cancersincluding thyroid cancers. These holdpromise and can be advocated onexperimental basis in the patients withlife threatening disease unresponsive tothe available treatmentmodalities.Targeted therapies can beOncogene inhibitor(tyrosine kinaseinhibitors ,RAS,RAF and MEK kinase),Modulators of growth or apoptosis (Coxinhibitors,retinoids),Angiogenesis(VEGF) inhibitors,Immunomodulators & gene therapy 32 .Long term high dose octreotide treatmentin patients of medullary carcinoma thyroidhas shown beneficial effects in tumourbearing somatotastin receptors. 33References1. Harzog B. Thyroid gland diseases andtumors ; Surgical aspects.Prog.Ped.Surg.183;16;752. Beierwaltes WH,RabbaniR,Duochowski C,Lloyd RV,EyreP,MalletteS. Ananalysis of “Ablationof thyroid remanants” with I-131 in 511patients from 1947-1984;experience atUniversity of Michigan.J. Nucl. Med1984.;25;1287-933. Goolden AWG.The indications forablating normal thyroid tissue with I-131 in differentiated thyroid cancer.ClinEndocrino 1985;23;81-6,4. MazzaferiEL,YoungRL,Papillarythyroid carcinoma ;A 10 year follow upreport of the impact of therapy in 576patients .Am J Med 1981;70;511-5185.Livalsic VA. Well differentiated thyroidcarcinoma: review article. Clin Oncol1996;8:281-288.6.Beierwaltes WH.The treatment ofthyroid carcinoma with radioactive iodine.Semin Nucl Med 1978; 8:79.7.Maxon HR, Thomas SR ,Hertzbrg VSet al.Relation between radiation effectivedose and oucome of radioiodine therapyfor thyroid cancer.N Engl J Med1983;309:9378. Mazzaferri EL , Jhiang SM. Long termimpact of initial surgical and medicaltherapy on papillary and follicular thyroid66<strong>Journal</strong> of Postgraduate Medical Education, Training & ResearchVol. I, No. I & II
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Journal 1pages FINAL 34- - National Board Of Examination

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