Medullary thyroid carcinoma: prognosis of familial versus sporadic disease and the role of radiotherapy.

A retrospective study of 202 patients with medullary thyroid carcinoma (MTC) diagnosed between 1943 and 1987 was done to compare the prognosis of patients with sporadic disease and those with the familial form of multiple endocrine neoplasia type II and to study the effect of radiotherapy. Patients with multiple endocrine neoplasia type II had a significantly higher survival rate than did patients with the sporadic variety (P less than 0.005), but most patients with sporadic tumors were older and had more advanced disease. No differences in survival rates were found when patients from these 2 groups were matched for age and involvement of the thyroid gland only (P greater than 0.3), involvement of the thyroid gland plus cervical nodes (P greater than 0.3), and involvement of the thyroid gland, cervical nodes, and soft tissue (P greater than 0.7). When patients with MTC who received radiotherapy were matched for age, extent of disease, and surgery with patients who had had no radiotherapy, the latter group was found to live significantly longer (P less than 0.05). We conclude that 1) the apparently poor prognosis of patients with the sporadic variety of MTC may be related to the patients' older age at detection rather than to inherent differences in the two forms of disease, and 2) radiotherapy has little effect on MTC.