Pulmonary metastases in differentiated thyroid cancer: efficacy of radioiodine therapy and prognostic factors.

CONTEXT Data from a large cohort of patients with pulmonary metastases from differentiated thyroid cancer (DTC) were retrospectively analyzed. OBJECTIVE To assess the effect of radioiodine therapy and investigate the prognostic factors of survival for patients with pulmonary metastasis secondary to DTC. METHODS A total of 372 patients with pulmonary metastasis from DTC treated with (131)I entered the study. According to the results of (131)I whole-body scan (WBS), pulmonary metastases were classified as (131)I-avid and non-(131)I-avid. For patients with (131)I-avid lung metastases, treatment response was measured by three parameters: serum thyroglobulin (Tg) levels, chest computed tomography (CT) and post-therapeutic (131)I-WBS. Overall survival was calculated by the Kaplan-Meier method. Factors predictive of the outcome were determined by multivariate analyses. RESULTS Among patients demonstrating (131)I-avid pulmonary metastases (256/372, 68.8%), 156 cases (156/256, 60.9%) showed a significant decrease in serum Tg levels after (131)I therapy and 138 cases (138/229, 60.3%) showed a reduction in pulmonary metastases on follow-up CT. A complete cure, however, was only achieved in 62 cases (62/256, 24.2%). Multivariate analysis showed that only age, the presence of multiple distant metastases and pulmonary metastatic node size were significant independent variables between the groups of (131)I-avid and non-(131)I-avid. CONCLUSION This study indicated that, most (131)I-avid pulmonary metastases from DTC can obtain partial or complete remission after (131)I therapy. Younger patients (<40 years old) with only pulmonary metastases and small ('fine miliaric' or micronodular) metastases appear to have relative favorite outcomes. Patients who do not respond to (131)I treatment have a worse prognosis.