Purpose: Thymoma is a rare disease. The treatment of patients with invasive thymoma remains controversial. The prognosis of such patients is poor, even with the use of postoperative radiation therapy and chemotherapy. We retrospectively reviewed the outcome and prognostic factors in a series of 90 patients presenting with an invasive thymoma treated by partial resection or biopsy and radiation therapy.
Methods and materials: From 1979-1990, 163 patients with the diagnosis of lymphoepithelial thymoma were treated in 10 French cancer centers. Patients were staged using the postoperative "GETT" classification derived from that of Masaoka. Ninety patients who presented with an invasive thymoma, 58 Stage III (21 IIIA: partial resection and 37 IIIB: biopsy) and 32 Stage IVA (intrathoracic thymoma spread), are the subject of this report. Treatment combined surgery and radiation therapy (+/- chemotherapy), with curative intent. Surgery consisted of partial resection in 31 patients (21 Stage III), and biopsy in 55 patients (37 Stage III). The median radiation dose to the tumor was 50 Gy (30-70 Gy). Supraclavicular radiation was performed in 59 patients (median dose 40 Gy). Chemotherapy, combined with radiation in 59 patients, consisted of multidrug regimens, mainly platinum based.
Results: The median follow-up is 105 months (20-165 months). The 5- and 10-year overall survival rates are 51 and 39%, respectively. There is a great impact of the extent of surgery on survival: the 5- and 10-year survival rates were 64% and 43%, respectively, after partial resection, compared to 39% and 31% after biopsy (p < 0.02). Local control at 8.5 years was obtained in 59 of 90 patients (66%): 40 Stage III, 19 Stage IVA. There is a significant relationship between the extent of surgery and the local control (16% of relapse after partial resection vs. 45% after biopsy, p < 0.05). Seven patients developed significant (grades 3-4 WHO grading system) treatment-induced side effects. Stage, histologic type, and chemotherapy were not prognostic factors.
Conclusion: In this large multicentric retrospective study of invasive thymomas (Stage III-IVA) treated by surgery and radiation, results show the importance of loco-regional treatments, such as surgery and radiation therapy. There is also a great impact of radiation on local control. However, the rate of local recurrence (34%) justifies recommending a higher dose of radiation (> 50 Gy) than doses used in this study, for incompletely resected patients. The role of chemotherapy needs to be further assessed.