[131 iodine and differentiated thyroid cancers]

By its dual gamma and beta emission, 131I permits both external detection and selective irradiation of residual or metastatic differentiated thyroid carcinoma. Indications based on the evaluation of prognostic factors and on the quality of surgical excision are more advisable than systematic use. Useless, even harmful after unilateral surgery decided because of a very good prognosis, 131I is recommended according to several retrospective studies for post surgical ablation of the remnants, the detection and the treatment of the recurrences and the distant metastases. The use of therapeutic doses in patients with an isolated elevation of thyroglobuline (Tg) without any clinical or radiological signs favors early diagnosis and cure of metastases with negative diagnostic scintigraphy. Dosimetric considerations and radioprotection measures must be guided by specific rules concerning radiometric material, adapted rooms and skilful personnel. Scintigraphic detection must be done in the best technical conditions. Protracted follow-up is based on Tg dosages and 131I whole body scintigraphies. Early diagnosis of metastases and positive response to 131I irradiation influence favorably remission rates. Even if a complete remission is not achieved, repeated treatments by a specialized team improve the quality of survival for metastatic patients.