Results of postoperative radiation therapy in medullary carcinoma of the thyroid: a retrospective study by the French Federation of Cancer Institutes--the Radiotherapy Cooperative Group.

Between 1971 and 1989, 59 patients received external radiation therapy with a curative intent. There were 25 females and 34 males, ranging in age from 19 to 87. No patients had distant metastasis at the onset of treatment. The majority of patients had a total thyroidectomy (55/59), generally combined with neck dissection. Residual tumour was left in 11 cases, and 44 patients had positive cervical nodes. Using megavoltage radiotherapy, the whole neck and the upper mediastinum area were most often irradiated through a large anterior Y-shaped field without laryngeal shielding. The mean dose to the tumoral bed was 54 Gy. Dysphagia was observed in 32 patients (11, 17 and 5 scores were grade 1, 2 and 3, respectively). Dyspnea occurred in five cases and in two of these cases, it was considered to be severe. Local recurrences were noted in 18 (30%) patients, most of them occurring within the fields of irradiation. Parameters such as age, sex, total dose, irradiated volumes or cervical node enlargement did not modify the local control rate. The same conclusions can be drawn for distant failures. Thirty five patients are still alive and among them, 24 have no evidence of disease. The average length of survival is 70.5 months and is shortened by the occurrence of distant failures except in patients with bone metastases.