The Role of Adjuvant Radiation Therapy for Resected Stage III Thymoma: A Population-Based Study

Background Because of the rarity of the disease and long survival of most patients, the role of adjuvant radiation therapy in patients with surgically resected stage III thymoma is unclear, and few prospective studies are available. The objective was to evaluate the impact of postoperative radiation therapy after resection of stage III thymoma. Methods The Surveillance, Epidemiology, and End Results (SEER) database was queried for all patients with stage III thymoma who underwent surgical therapy and survived more than 30 days after diagnosis. Survival was estimated with the Kaplan-Meier method. The hazard ratio for death was determined using a Cox proportional hazard model. Results There were 476 patients with stage III thymoma identified who underwent surgical therapy, did not receive preoperative radiotherapy, and had complete SEER records with regard to radiation treatment. Postoperative radiation therapy was given to 322 patients (67.6%). Patients who received postoperative radiation therapy were younger and had a higher rate of debulking surgery than patients who did not. Patients receiving postoperative radiation had a median overall survival of 127 months (95% confidence interval, 100.9 to 153.1) compared with 105 months (95% confidence interval, 76.9 to 133.1) in patients treated with surgery alone ( p = 0.038). However, in multivariate analysis, postoperative radiation was not a significant factor affecting overall survival. Disease-specific survival was significantly improved in the adjuvant radiation group, and in multivariate analysis, improved outcomes were associated with postoperative radiation ( p = 0.049). Conclusions In this large population-based study, most patients with stage III thymoma were treated with adjuvant radiation. Postoperative radiation was associated with improved disease-specific survival, but not improved overall survival.