Association of adjuvant radioactive iodine therapy with survival in node-positive papillary thyroid cancer

Purpose: To assess the effect of adding radioactive iodine (RAI) therapy to total thyroidectomy (TT) on overall survival (OS) in patients presenting with papillary thyroid cancer (PTC) and cervical pathologically proven LN metastases (pN1). Methods and materials: We identified a cohort of patients with PTC and nodal metastases treated with TT alone or TT plus RAI in the Surveillance, Epidemiology and End Results database between 2004 and 2013. Propensity score 1-to-1 matching was used to balance baseline characteristics. Cox proportional hazards regression models and Kaplan-Meier survival analysis were used to test the relationship between RAI and OS. Results: In all, 15,953 patients were identified. After propensity score matching, 12,128 patients remained in each group. Based on multivariate Cox analysis, patients treated with TT + RAI had a statistically significant improvement in OS compared with those treated with TT alone [hazard ratio (HR) = 0.54, P < 0.001)], and significance persisted in the matched cohort (HR = 0.41, P < 0.001). In a subgroup analysis, the survival benefit was observed among patients 55 years but not among those < 55 years (age < 55: HR = 1.06, P = 0.72; age >= 55: HR = 0.33, P < 0.001). Patients with stage T4 benefited most from RAI treatment (HR = 0.29, P < 0.001). Conclusion: This propensity-matched analysis suggests that RAI therapy after TT was associated with improved OS in PTC patients with pN1 disease. Adjuvant RAI therapy needs to be considered in this patient group.