Prognostic indicators of outcomes in patients with lung metastases from differentiated thyroid carcinoma during long-term follow-up

Background: Distant metastases, although uncommon, represent maximum disease-related mortality in differentiated thyroid carcinoma (DTC). Lungs are the most frequent sites of metastases. We aimed to evaluate long-term outcomes and identify prognostic factors in metastatic DTC limited to the lungs. Methods: This retrospective study included 89 patients with DTC and metastases limited to the lungs, who were treated between 1996 and 2012 at Samsung Medical Center. Progression-free survival (PFS) and cancer-specific survival (CSS) rates were evaluated according to clinicopathologic factors. Cox regression analysis was used to identify independent factors associated with structural progressive disease (PD) and cancer-specific death. Results: With a median follow-up of 84 months, the 5- and 10-year CSS rates were 78% and 73%, respectively. Older age at diagnosis (≥55 years), radioactive iodine (RAI) nonavidity, preoperative or late diagnosis of metastasis and macro-nodular metastasis (≥1 cm) were predictive of decreased PFS and CSS. Multivariate analysis identified older age (P =.002), RAI nonavidity (P =.045) and preoperative (P =.030) or late diagnosis (P =.026) as independent predictors of structural PD. RAI avidity was also independent predictor of cancer-specific death (P =.025). Conclusion: Patients with DTC and metastatic disease limited to the lungs had favourable long-term outcomes. Age, RAI avidity and timing of metastasis were found to be major factors for predicting prognosis.