Therapy for thymic epithelial tumors: a clinical study of 1,320 patients from Japan.

BACKGROUND: Surgery remains the mainstay of treatment for thymic epithelial tumors, and radiation and chemotherapy also have been applied widely as adjuvant and palliative procedures.
METHODS: We compiled records of 1,320 patients with thymic epithelial tumors who were treated from 1990 to 1994 in 115 institutes certified as special institutes for general thoracic surgery by The Japanese Association for Chest Surgery.
RESULTS: Patients with stage I thymoma were treated with only surgery, and patients with stage II and III thymoma and thymic carcinoid underwent surgery and additional radiotherapy. Patients with stage IV thymoma and thymic carcinoma were treated with radiation or chemotherapy. The Masaoka clinical stage is an excellent predictor of the prognosis of thymoma and thymic carcinoma, but not thymic carcinoid. In stage III and IV thymoma, the 5-year survival rates of total resection, subtotal resection, and inoperable groups were 93%, 64%, and 36%, respectively. On the other hand, in thymic carcinoma, the 5-year survival rates of total resection, subtotal resection, and inoperable groups were 67%, 30%, and 24%, respectively. Prophylactic mediastinal radiotherapy could not prevent local recurrences effectively in patients with totally resected stage II and III thymoma. Adjuvant therapy including radiation or chemotherapy did not improve the prognosis in patients with totally resected III and VI thymoma and thymic carcinoma.
CONCLUSIONS: Total resection is the most important factor in the treatment of thymic epithelial tumors. There is value in debulking surgery in invasive thymoma, but not in thymic carcinoma. We doubt that adjuvant therapy is valuable for patients with totally resected invasive thymoma and thymic carcinoma.