Postoperative Radiation Therapy After Complete Resection of Thymoma Has Little Impact on Survival

BACKGROUND: Postoperative radiation therapy for thymoma is widely used, although the clinical benefits are controversial. Furthermore, to the authors' knowledge, the relation between postoperative radiation therapy and cell type classified by the World Health Organization (WHO) is not known. METHODS: The records of 324 patients (ages 17-83 years; mean, 51 years; 160 males and 164 females) who underwent complete resection of a thymoma between 1970 and 2005 were reviewed. Mediastinum postoperative radiation therapy was performed for 134 patients. Survival rates and patterns of recurrence were determined according to Masaoka stage and WHO cell type. RESULTS: The 10-year disease-specific survival rates for patients with and without postoperative radiation therapy were 92.8% and 94.4%, respectively (P = .22). Subset analyses after stratifying by Masaoka stage and WHO cell type demonstrated that the 10-year disease-specific survival rate for patients without postoperative radiation therapy with Masaoka stage I and II, as well as those with WHO cell types A, AB, or B1, was 100%, which was satisfactory. Furthermore, the rates for patients with Masaoka stage III/IV and those with WHO cell types B2/B3 with or without postoperative radiation therapy were not found to be significantly different. In 24 patients with disease recurrence, pleural dissemination was observed most often, followed by distant metastases; local disease recurrence without other recurrence occurred in 2. CONCLUSIONS: The authors concluded that surgical resection alone is sufficient for thymoma patients with Masaoka stage I and II, and those with WHO cell types A, AB, and B1. Furthermore, an optimal treatment strategy should be established for patients with Masaoka stage III/IV and WHO cell type B2/B3 thymomas. Cancer 2009;115:5413-20. (C) 2009 American Cancer Society.