Long-term outcomes and prognostic factors of patients with lung metastases from differentiated thyroid cancer after radioiodine therapy in Japan

Long-term survival in patients with differentiated thyroid cancer (DTC) and lung metastasis remains unexplored in Japan. This study aimed to investigate the long-term survival and prognostic factors of radioiodine therapy (RIT) in a University Hospital setting. This retrospective study included 62 patients with lung metastases from DTC who received RIT between March 2005 and December 2016. According to the I-131 whole-body scan and chest computed tomography results, lung metastases were classified as I-131-avid or non -I-131-avid, and miliary, micronodular, or macronodular metastases. The 5 -and 10-year overall survival (OS) rates from the initial RIT were calculated by the Kaplan-Meier method, and a proportional hazard fit analysis was performed to determine prognostic factors. With a median follow-up of 7.9 years, the 5-and 10-year OS rates from the initial RIT were 93% and 72%, respectively. Univariable and multivariable analyses of patient subgroups revealed that macronodular lung metastases (defined as nodules >1 cm), older age at initial RIT, and high thyroglobulin values (>400 ng/mL) at initial RIT predicted low OS. The 5-and 10-year OS rates of DTC patients with lung metastases were similar to those in previous Japanese reports, which included a smaller sample size compared with ours. Patients with = 1 cm lung metastases, aged = 55 years, and a thyroglobulin level of = 400 ng/mL at the initial RIT had favorable outcomes.