Postoperative Radiotherapy for Completely Resected Stage II or III Thymoma

Introduction: We assessed the efficacy of adjuvant radiotherapy (RT) in patients with stage II or III thymoma and evaluated the prognostic factors after the treatment. Patients and Methods: The medical records of 76 patients with completely resected stage II (n = 65) or III (n = 11) thymoma treated at a single institution within the period from November 1988 to February 2009 were retrospectively reviewed. Seventeen patients were treated with surgery only (group A), and 59 patients received adjuvant RT after surgery (group B). The median radiation dose was 50 Gy (range: 43.2-66 Gy). The prognostic factors, such as age, myasthenia gravis symptom, tumor size, staging, adjuvant RT, and radiation dose, were analyzed. The median follow-up time was 58.5 months (range: 6-231 months). Results: The 5- to 10-year overall survival and disease-free survival (DFS) rates were 95.3% and 83.8% and 91.5% and 82.5%, respectively. The 5- and 10-year DFS (80% and 70% and 97.8% and 92.7% in groups A and B, respectively; p = 0.043), and the median time to recurrence (37.4 and 50.6 months in groups A and B, respectively) was statistically different between groups A and B. Conclusion: Masaoka staging and adjuvant RT were related to DFS in completely resected stage II or III thymoma. Based on this study, adjuvant RT will be beneficial in this clinical setting.