Radioactive iodine in the treatment of medullary carcinoma of the thyroid.

To determine the value of adjunct 131I therapy in medullary carcinoma of the thyroid (MCT), two groups of patients with histologically proved MCT were studied. Group A consisted of 15 patients (6 men and 9 women) treated by surgery, followed by an ablative dose of 131I, and group B included 84 patients (39 men and 45 women) treated by surgery alone. Patients in group A were followed for 1.5-14 yr (median, 53 months), and those in group B were followed for 1-27 hr (median, 75 months). Seven patients (46.6%) from group A and 36 patients (42.9%) from group B developed recurrence or metastasis. The 5- and 10-yr survival rates were 87.5% and 75% for group A and 89% and 74% for group B; the difference was not significant (P greater than 0.05). The changes in serum calcitonin levels in 4 patients of group A were not different from those in patients who did not receive 131I. We conclude that 131I has no value as an adjunct to surgery in the management of MCT.