Invasive thymoma: the role of mediastinal irradiation following complete or incomplete surgical resection.

To evaluate the role of mediastinal irradiation (RT) following surgery for invasive thymomas, a clinical and pathologic review of 117 patients with the diagnosis of thymoma was completed. Fourteen cases were excluded because of the lack of histologic criteria for a thymic tumor, and the remaining 103 were classified according to a staging system as follows: stage I, completely encapsulated (43); stage II, extension through the capsule or pericapsular fat invasion (21); stage III, invasion of adjacent structures (36); and stage IV, thoracic dissemination or metastases (3). The 5-year actuarial survival and relapse-free survival rates were 67% and 100% for stage I, 86% and 58% for stage II, and 69% and 53% for stage III. No recurrences occurred among stage I patients after total resection without RT. However, eight of 21 patients with invasive (stage II or III) thymomas had mediastinal recurrence as the first site of failure following total resection without RT. The 5-year actuarial mediastinal relapse rate of 53% in this group compares unfavorably with the mediastinal relapse rate seen among stage II or III cases following total resection with RT (0%) or following subtotal resection/biopsy with RT (21%). Despite attempted salvage therapy, five of eight patients with mediastinal relapse following total resection alone died of progressive disease. No significant difference was observed in the local relapse rate, overall relapse rate, or survival between those patients undergoing biopsy and RT v subtotal resection and RT for invasive thymomas (stages II and III). Total resection alone appears to be inadequate therapy resulting in an unacceptably high local failure rate with poor salvage therapy results.