Role of Postoperative Radiotherapy in Nonlocalized Thymoma Propensity-Matched Analysis of Surveillance, Epidemiology, and End Results Database

Introduction: Because of a lack of randomized trials, the role of postoperative radiotherapy (PORT) in thymomas has not been established. This study evaluated the prognostic impact of the adjuvant treatment in surgically resected nonlocalized thymomas. Methods: Patients diagnosed between 2000 and 2010 were identified from the Surveillance, Epidemiology, and End Results database (1973-2011 registry). Cases with localized or organ-confined tumors were not included. Propensity-matched analysis was conducted considering baseline characteristics. Results: A total of 529 patients were identified. The median age was 57 years (range, 18-86), and 345 (65%) patients received PORT. Before and after propensity score matching, overall survival (OS; p = 0.018 and 0.008, respectively) and disease-specific survival (DSS; p = 0.007 and 0.008, respectively) were better in the PORT group. In multivariate analyses of the matched population, no receipt of PORT induced poorer OS (hazard ratio [HR], 1.98; 95% confidence interval [CI], 1.27-3.09) and DSS (HR, 2.64; 95% CI, 1.32-5.29). Primary tumor extensions of adjacent organs or structures and further contiguous extensions also resulted in worse outcomes (p < 0.001 and equal to 0.039 for OS; p = 0.006 and 0.009 for DSS, respectively). In the subgroup analyses, PORT was associated with favorable OS in stages III and IV (p = 0.049 and 0.012, respectively) and DSS in stage III (p = 0.005). Conclusion: Regarding the independent prognostic significance of PORT, this population-based analysis demonstrates the survival benefits of PORT in relation to nonlocalized thymomas. We recommend consideration of PORT in the poor prognostic subset of stages III to IV in the contemporary era.