Role of adjuvant radiotherapy for stage II thymoma after complete tumor resection.

To determine whether patients with Masaoka stage II thymoma benefit from adjuvant radiation therapy after complete tumor resection.A total of 107 patients with stage II thymoma who underwent complete resection of their tumors between September 1964 and October 2006 were retrospectively analyzed. Sixty-six patients were treated with adjuvant radiotherapy, and 41 patients received surgery alone.Eight patients (7.5%) had a relapse of their disease, including two patients (4.5%) who had surgery alone, and 6 patients (9.5%) who had adjuvant radiation therapy. Disease-free survival rates at 5 and 10 years were 92.3% and 82.6%, respectively, for the surgery-plus-radiation group, and 97.6% and 93.1%, respectively, for the group that underwent surgery alone (p = 0.265). Disease-specific survival rates at 5 and 10 years were 96.4% and 89.3%, respectively, for the surgery-plus-radiation group and 97.5% and 97.5% for the surgery group (p = 0.973). On univariate analysis, patients with type B3 thymomas had the lowest disease-free survival rates among all subtypes (p = 0.001), and patients with large thymomas (>7 cm) had lower disease-specific survival rates than those with small tumors (<7 cm) (p = 0.017). On multivariate analysis, histological type (type B3) thymoma was a significant independent prognostic factor.Adjuvant radiotherapy after complete tumor resection for patients with stage II thymoma did not significantly reduce recurrence rates or improve survival rates. Histological type (type B3) thymoma was a significant independent prognostic factor. Further investigation should be carried out using a multicenter randomized or controlled study.