Efficacy and Survival Analysis of 131I Therapy for Bone Metastases from Differentiated Thyroid Cancer

Objective: Our objective was to investigate the clinical efficacy of I-131 therapy for bone metastases from differentiated thyroid cancer (DTC) and prognostic factors as well as to assess patient survival and variables influencing survival. Methods: One hundred six DTC patients with bone metastases treated with I-131 were retrospectively analyzed. The therapeutic efficacy was evaluated based on the change in serum thyroglobulin (Tg), the palliation of bone pain, and the anatomical imaging changes in bone lesions. The overall survival rates were estimated using the life-table method. Results: After I-131 therapy, a significant decrease in serum Tg was seen in 37 cases (34.9%), and serum Tg remained stable in 56 patients (52.8%). Among the 61 patients with painful bone metastases, 39 patients obtained a significant relief of bone pain, and the effective rate was 63.9%. The majority of DTC patients (76.4%) exhibited no obvious anatomical imaging changes in metastatic bone lesions after I-131 therapy. Only histopathological type and whether combined with nonosseous distant metastases had statistically significant impacts on changes in serum Tg (P = 0.009 and 0.023), and age over 45 yr and papillary thyroid carcinoma had favorable response on changes in anatomical imaging (P = 0.027 and 0.014). The 5- and 10-yr survival rates were 86.5 and 57.9%, respectively. Multivariate analyses showed that the presence of solitary bone metastases, only bone metastases, and I-131 therapy with previous bone surgery were independent factors associated with a better prognosis (P = 0.024, 0.009, and 0.031). Conclusion: I-131 therapy is a feasible and effective treatment for DTC bone metastases. A better prognosis can be accomplished in patients who had a single metastatic lesion, only bone metastasis, or underwent bone surgery before I-131 therapy. (J Clin Endocrinol Metab 96: 3078-3086, 2011)