Results of radioiodine treatment for distant metastases of differentiated thyroid carcinoma

To evaluate the effectiveness of raioiodine treatment for metastatic thyroid carcinoma, we reviewed results of radioactive iodine treatment in patients with functional lung or bone metastases. Of 760 patients who were treated for differentiated thyroid cancer between 1984 and 1998, we detected pulmonary metastases and bone metastases in 76 patients (10.0%) and 20 patients (2.6%), respectively. Among them, we could evaluated the effectiveness of I-131 therapy in 53 patients with lung metastases and 15 patients with bone metastases. Of 53 patients who received I-131 therapy with a mean cumulative dose of 26.2 GBq (1.1-84.4 GBq) for pulmonary metastases, metastatic lung lesions completely resolved in 19 patients (35.8%) and improved in 22 patients (41.5%). In 13 of 19 patients with complete remission of pulmonary metastases, the total accumulated dose of I-131 was less than 18.5 GBq. We found 43 sites of metastatic bone lesions in 15 patients with bone metastases. Of 29 lesions which received I-131 therapy, metastatic lesions improved in 14 sites (48.3%), but did not change or progress in 15 sites (51.7%) despite the I-131 therapy. Three lesions were completely cured with a combination treatment of surgery(± external radiotherapy) and I-131 therapy, and the other 11 lesions improved. Radioactive iodine treatment gives favorable results for pulmonary metastases. However, for bone metastases, there might be a need to use combination therapy including I-131 and surgery or external irradiation.=20