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.