A phase II evaluation of ifosfamide and mesna in unresectable diffuse malignant mesothelioma. A Southwest Oncology Group study.

Background. Malignant mesothelioma is a highly treatment-resistant neoplasm. This study represents an attempt to define an effective form of systemic therapy. Methods. Twenty-six patients with unresectable diffuse malignant mesothelioma were enrolled in Southwest Oncology Group (SWOG) study 8731 and treated with ifosfamide, 2 g/m2 intravenously for 4 days, and mesna 2 g/m2 intravenously for 5 days, every 3 weeks. Patients were either previously untreated with chemotherapy or had at most one prior systemic treatment. Results. Two patients, or 8% (95% confidence interval, 1-25%), achieved partial response, with response durations of 4 and 6 months. One additional patient met criteria for tumor size reduction but not duration criteria. Thirteen (50%) patients had stable disease of 4 months' median duration (range, 1-13 months). The median survival of the entire group was 6.5 months. The dose-limiting toxicity was granulocytopenia (11 patients, ≤ 250/μl). Conclusions. Ifosfamide/mesna has modest activity in malignant mesothelioma. It could be tested using alternate dosage schedules and in combination with other agents in treating this highly resistant neoplasm.