Postoperative radiotherapy of patients with thymic epithelial tumors (TET): a retrospective analysis of outcome and toxicity.

PURPOSE: The purpose of this study was to evaluate postoperative radiotherapy regarding outcome and toxicity in patients with thymic epithelial tumors (TET) after surgery. MATERIALS AND METHODS: We retrospectively analyzed medical records of 41 patients with TET treated with postoperative radiotherapy at our institution between 1995 and 2012. The impact of prognostic factors (e.g., Masaoka stage, histological subtype) was investigated and radiation-related toxicity was assessed. RESULTS: Median age was 59.8 years and median follow-up was 61 months. In 24.4 %, TETs were associated with paraneoplastic syndromes. The 5-year overall survival (OS) was 89.5 % and the 5-year disease-free survival (DFS) was 88.9 %. Masaoka stage had a significant impact on OS (p = 0.007). Locally limited stages I + II had a 5-year OS of 100 % compared to 80 % for stage III and 66.7 % for stage IV. The 5-year DFS was excellent with 100 % for both WHO groups A/AB/B1 and B2, respectively, and significantly (p = 0.005) differed from B3/C-staged patients with a 5-year DFS of 63.6 %. Resection status, paraneoplastic association, radiation dose, or tumor size did not influence survival. There were no high-grade acute or late side effects caused by radiotherapy. CONCLUSION: Masaoka stage has a significant impact on OS as WHO type has on DFS in patients with TETs after surgery and adjuvant irradiation. Postoperative radiotherapy with doses around 50 Gy is safe and not likely to cause high-grade toxicity. Further prospective trials are necessary to separate patient subgroups that benefit from radiotherapy from those that do not.