Radiotherapy of thymoma. Study of the literature apropos of a retrospective and multicenter series of 149 cases]

Thymomas is a rare disease. Staging systems and surgical adjuvant treatments remain controversial. We retrospectively reviewed the outcome and the prognostic factors in a series of 149 patients with non metastatic thymomas treated in ten French cancer centers between 1979 and 1990. Patients were staged according to the "GETT" classification derived from that of Masaoka. There were 13 stage I patients, 46 stage II, 58 stage III and 32 stage IV. Surgery consisted of complete resection in 63 patients, partial resection in 31 patients and biopsy alone in 55 patients. All patients received postoperative radiation therapy and 74 were given postoperative chemotherapy. Median follow-up was 7.7 years. Local control was obtained in 117 patients (78.5%) and was influenced by the extent of surgery (p < 0.0001). Metastases occurred in 26 patients. Seven patients developed grade 3-4 pulmonary and heart complications. One patient developed a malignant lymphoma after 24 cycles of chemotherapy. Disease-free survival (DFS) rates were of five years 92%, 75%, 60%, 39% and 48% in stage I, II, IIIA, IIIB and IVA patients, respectively. After complete resection, partial resection and biopsy alone, these rates were 74%, 60% and 38%, respectively. With a multivariate analysis, DFS rates were influenced by the extent of surgery (p < 0.001) and by chemotherapy (p < 0.001). Three other factors could predict a worse DFS: young age (p < 0.006), stages III-IV (p < 0.04) and mediastinal symptoms (p < 0.001), "GETT" staging correlated well with local control and survival. After complete resection, a 50 Gy postoperative radiation therapy can be recommended in patients with invasive thymomas. Despite a 65% local control rate after partial resection or biopsy alone in this series, a higher dose of radiation (> 60 Gy) must be evaluated. Despite the benefit of the chemotherapy in this retrospective and multicentric study, the role of this treatment remains to be assessed.