Postoperative radiotherapy in thymic carcinoma: treatment results and prognostic factors

To analyze the treatment results and prognostic factors of patients with primary thymic carcinoma treated by total or subtotal tumor resection followed by radiotherapy alone.

Between October 1987 and October 1997, 26 patients with thymic carcinoma were treated with complete or incomplete surgical resection and postoperative adjuvant irradiation without chemotherapy. The radiation was delivered with 10-MV X-ray given 5 days per week at 1.8 to 2 Gy per fraction. Total doses ranged from 40 to 70 Gy. All patients had at least 40 months of follow-up.

The 5-year overall survival rate, local control rate, and distant metastasis-free rate were 77%, 91%, and 57%, respectively. Several prognostic factors, including sex, age, extent of resection (total resection vs. subtotal resection), Masaoka staging (early Stage I + II vs. advanced Stage III + IV), pathology (low-grade vs. high-grade), and postoperative radiation dose (> or =60 Gy vs. <60 Gy), were evaluated in univariate analysis. The Masaoka staging system was the only statistically significant predictor in overall survival rate (p = 0.0482) and distant metastasis-free rate (p = 0.0193).

The Masaoka staging system is the most important prognostic factor in primary thymic carcinoma patients receiving postoperative radiotherapy alone. For resectable tumors, surgery and postoperative radiotherapy can achieve good local control, but the distant metastatic rate is still high. Further investigation of more effective chemotherapy is needed.