Thymoma: prognostic factors and treatment outcomes

The objective of this study was to establish prognostic factors for thymoma and determine the impact of surgery with or without postoperative radiotherapy.

Seventy patients treated at the University Hospital Düsseldorf during the period 1954-1991 were retrospectively studied. All thymoma patients underwent surgery, 22 received postoperative radiotherapy, and 3 also received chemotherapy. According to thymoma staging as described previously by Masaoka et al., 21% were Stage I, 26% Stage II, 43% Stage III, 7% Stage IVA, and 3% Stage IVB. Lymphocytic type disease was found in 36% of patients, lymphoepithelial type in 33%, epithelial type in 23%, and spindle cell type in 9%. The relevance of Karnofsky performance status (KPS), gender, age, myasthenia gravis, histology, tumor size, and stage to survival was determined by univariate analysis, and their independent significance was tested by multivariate analysis. Survival rates were calculated using the Kaplan-Meier method and the log rank test.

In univariate analysis, KPS (P < 0.001), histologic type (P=0.0093), and stage (P=0.0001) proved to be significant predictors of overall survival. Spindle cell type was associated with the best and epithelial type the worst prognosis; patients with the latter type had a 5-year survival rate of 30%. Multivariate analysis revealed that stage, histology, and KPS were predictive of overall survival. In Stages III and IV, relapses were reduced by postoperative radiotherapy from 50% to 20%. The site of relapse was outside the irradiated area in 80% of patients. Disease free survival (P=0.36) and median survival (P=0.72) of patients with completely resected advanced thymomas did not differ from that for patients with incompletely resected tumors who received radiotherapy.

Postoperative radiotherapy can improve local control in patients with advanced thymoma. Survival after incomplete resection is not compromised when postoperative radiotherapy is employed. KPS should be considered an important prognostic factor in future studies.