[Role of radiotherapy in the treatment of medullary cancer of the thyroid].

Medullary thyroid carcinoma (MTC) is a rare tumor for which the main treatment is surgery. However, external radiation therapy (RT) plays an important part in well-defined patients. Out of the 115 patients with MTC treated at the Institute Gustave Roussy: Thirty-five MTC patients with residual cervical disease and without distant metastases had their thyroid region irradiated (60Co, 45 to 50 Gy in 5 weeks). The overall survival of these patients is similar to that of patients with limited cervical extension (n = 57) treated by surgery alone. The results of this study show the effectiveness of cervico-mediastinal irradiation treatment for MTC with extensive local tumor after incomplete surgery. Eight MTCs with inoperable cervical tumor were treated only by external RT. Median survival was 44 months. In six of them, long-term local control was observed: three are alive at 52, 62 and 70 months and 3 died from distant metastases at 36, 36, and 117 months after treatment. Sixteen MTCs with distant metastases were treated with RT on bone metastases (n = 10) or compressive lymph node metastases (n = 6) with good palliative effect. This study shows the efficacy of post-operative external RT in MTCs with extensive cervical tumors, as a curative treatment in non-surgically eradicable cervical tumors and as a palliative treatment for metastatic localisations. The technique of cervico-mediastinal RT is discussed.