Adjuvant Radiotherapy for Completely Resected Stage 2 Thymoma

BACKGROUND: The clinical benefit of postoperative mediastinal radiation for completely resected Masaoka stage 2 thymoma remains controversial. Due to its indolent nature and infrequent recurrences, no study has definitively determined the optimal approach. METHODS: We retrospectively reviewed 175 consecutive patients who underwent thymic resection from January 1990 to July 2008 at the University of Pennsylvania. The primary endpoint was local recurrence, defined as recurrence within the surgical bed, treated by resection alone versus resection plus radiation. Patients with high recurrence risk were referred for adjuvant radiotherapy. RESULTS: Seventy-four Masaoka stage 2 patients were resected; 62 underwent complete resections with adequate postsurgical follow-up. Thirty-seven patients received adjuvant radiotherapy and 25 patients were observed. The median radiation dose was 5040 cGy. The median follow-up for all patients was 52 months. The local recurrence rate was 3.2%. The proportion of recurrences in patients observed after surgery was 8% versus 0% in those who received adjuvant radiotherapy (P = .15). Size was not an independent predictor of recurrence (P = .81). The tumor-related death rate was 0%, and overall death rate was 3.2%. One death occurred in each group, observation, and radiation. There were no grade 3 or 4 complications with radiation. CONCLUSIONS: Recurrence rates were low following resection of stage 2 thymoma either with or without adjuvant radiotherapy. Adjuvant radiotherapy, although well-tolerated, did not significantly decrease the local relapse rate. Differences may be observed in future studies of patients who are at higher risk for local recurrence, based on completeness of resection, World Health Organization histology, and tumor size. Cancer 2011;117:3502-8. (C) 2011 American Cancer Society.