Is it still worthwhile to treat bone metastases from differentiated thyroid carcinoma with radioactive iodine?

From 1964 to 1989, bone metastases were found in 28 of 600 patients operated on for differentiated thyroid carcinoma. Bone metastasis was the presenting symptom in 15 (54%) patients, was detected from the initial symptom in 4 (14.5%) patients, and occurred subsequently in 9 (32%) patients, with an average lag time of 4.5 years after surgical treatment. Pathological pattern of the thyroid cancer was follicular in 26 (93%) patients and papillary in 2 (7%) patients. Bone metastatic involvement was multiple in 21 (75%) patients and associated with other synchronous or metachronous distant metastases in 13 (46%) patients, especially in the lung (10 patients) or the brain (3 patients). The primary treatment of thyroid carcinoma was total thyroidectomy in all 28 patients, with additional modified neck dissection in 8 patients. All 15 patients presenting with symptoms had bone metastases demonstrated by x-ray studies. Six of the bone metastases only took up radioactive iodine 6 weeks after total thyroidectomy, as did 2 of 4 bone metastases detected at initial observation and 4 of 9 metachronous bone metastases. All 12 patients with functioning bone metastases were given radioactive iodine therapy; 4 of the metastases were surgically resected. Only 2 patients with bone metastases showed a complete response after an ablative dose of I-131; none of the metastases had been demonstrated by x-ray studies. Radioactive iodine therapy cures no more than 17% of patients with bone metastases taking up radioactive iodine and 7% of all patients with bone metastases. All patients cured of bone metastases were given radioactive iodine, either alone, or combined with other treatment.(ABSTRACT TRUNCATED AT 250 WORDS)