Radiotherapy for invasive thymoma and thymic carcinoma. Clinicopathological review

This study reports clinicopathological features and outcome of thymic tumors. Twenty-seven patients with invasive thymoma and 6 patients with thymic carcinoma who had received radiotherapy either primary or postoperatively were analyzed retrospectively.

All 33 patients were irradiated with a mean dose of 50 Gy after complete resection (16 patients), partial resection (9 patients) or biopsy (8 patients). Staging was done according to the Masaoka classification; there were 12 Stage II, 12 Stage III and 9 Stage IV patients.

In patients with invasive thymoma Stage II to IV (median follow-up 54.4 months) Kaplan-Meier estimates of overall survival (OS), disease-specific (DSS) and disease-free survival (DFS) at 5 years were 63.7% (95% confidence interval [CI], 42 to 84%), 88.3% (CI, 75 to 100%) and 77.4% (CI, 58 to 95%), respectively. Among the prognostic factors tested, such as age, myasthenia gravis, completeness of surgery and histologic subclassification, total radiation dose, and Masaoka Stage, the latter was the only significant predictor of improved survival (p = 0.04). Considering local control, radiation dose was a significant prognostic factor (p = 0.0006). In patients with thymic carcinoma (median follow-up 43.4 months) 5-year DSS, and DFS were 22.2% (CI, 0 to 60%) and 16.7% (CI, 0 to 46%), respectively. Thymoma as compared to thymic carcinoma had a statistically significant better DSS (p = 0.007) and DFS (p = 0.0007).

Postoperative radiotherapy with sufficient doses plays an important role as adjuvant treatment in complete or incomplete resected invasive Stage II to III thymoma. In unresectable thymoma Stage III to IV as well as in thymic carcinoma a multimodality approach should be considered to improve survival.