Phase II study of a multidisciplinary approach with induction chemotherapy, followed by surgical resection, radiation therapy, and consolidation chemotherapy for unresectable malignant thymomas: final report

Abstract

Purpose: To evaluate tumor resectability after induction chemotherapy and to determine disease-free and overall survival rates of patients with locally advanced unresectable thymoma that received a multimodal treatment regimen. Patients and methods: Twenty-two patients (9 men, 13 women) with histologically confirmed invasive thymoma were treated with a multidisciplinary regimen consisting of three courses of induction chemotherapy, surgical resection, and radiation therapy, followed by three courses of consolidation chemotherapy. The median age was 47 years (range, 25–70). Eleven patients had stage III disease, 10 patients, stage IVA, and one patient, IVB. The most common histologic type was lymphocytic. Induction chemotherapy consisted of 500 mg/m 2 of cyclophosphamide on day 1; doxorubicin (20 mg/m 2 per day) on days 1–3 via continuous infusion (a total of 60 mg/m 2); cisplatin (30 mg/m 2 per day) on days 1–3 (a total of 90 mg/m 2); and prednisone (100 mg per day) on days 1–5. This cycle was repeated three times at 3–4-week intervals. Patients then underwent surgery for tumor resection and received radiotherapy. Consolidation chemotherapy given at 80% of the induction chemotherapy doses of cyclophosphamide, doxorubicin, and cisplatin and 100% of the dose of prednisone was then repeated every 3–4 weeks for a total of three courses. Results: Induction chemotherapy produced major responses in 17 (77%) of the 22 patients including 3 (14%) complete responses (CR) and 14 (63%) partial responses (PR). Twenty-one patients underwent surgical exploration: 16 (76%) had complete resection and 5 (24%) had incomplete resection; one patient refused surgery. All 22 patients received radiation therapy. Nineteen of 22 patients completed the planned therapy, and all but one had completed consolidation chemotherapy at the time of analysis. With a median follow-up time of 50.3 months, 18 of the 19 patients who completed the multidisciplinary approach were disease-free. Of the 22 patients originally registered, 20 were alive at the time of analysis (one patient died of endocarditis, and one died of recurrent disease). The overall survival rate was 95% at 5 years (95% confidence interval (CI), 0.87–1.0) and 79% at 7 years (95% CI, 0.55–1.0). The progression-free survival rates were 77% at 5 years (95% CI, 0.58–1.0) and 77% at 7 years (95% CI, 0.58–1.0). The major side effect from induction and consolidation chemotherapy was myelosuppression. Nine patients experienced grade III/IV neutropenia, which included neutropenic fever in two patients, and grade III thrombocytopenia in two patients. The most common nonhematologic side effects were fatigue, nausea and vomiting, and decreased appetite. One patient experienced acute respiratory distress syndrome after surgical resection and required a prolonged hospitalization. No patients developed cardiac toxic effects, and no surgical mortality occurred. Conclusions: The use of induction chemotherapy to optimize surgical resectability of thymoma followed by radiation therapy and consolidation chemotherapy lead to good control of residual disease and high overall survival rates. We believe that this combined multidisciplinary approach prolongs lives and may cure locally advanced unresectable malignant thymomas. Future prospective multi-institutional studies are needed to further verify or define the best treatment for this patient population.