Results of radioiodine therapy in 47 patients with distant metastases of differentiated thyroid carcinoma

In the last ten years, 47 patients with distant metastases of differentiated thyroid carcinoma have been treated with 131I following total thyroidectomy. Post-therapy whole body 131I scans revealed detectable uptake in the metastatic lesions in 23 (62%) of 37 patients with lung metastases, 10 (67%) of 15 patients with bone metastases five (71%) of seven patients with mediastinal metastases, and neither of two patients with brain metastases. The concentration of 131I in the metastases was significantly correlated with serum T3 and T4 concentrations, and inversely correlated with serum TSH concentrations. Most of the patients with a strong positive scan were euthyroid, suggesting that thyroid hormones produced by the tumor compensated for hypothyroidism following total thyroidectomy. There was no significant relationship between serum thyroglobulin concentration during T4 replacement therapy and 131I uptake or the efficacy of therapy. Twenty patients with lung (54%), five with bone (33%), two with mediastinal (29%), and none with brain metastases showed tumor regression after treatment. Significantly increased 131I uptake in lung metastases, better therapeutic results and better prognosis were demonstrated in young patients. In conclusion, age, 131I whole body scanning and serum thyroid hormone concentrations are considered to be useful in predicting the efficacy of 131I treatment for distant metastases, especially in the lung.