Phase II study of continuous-infusion high-dose ifosfamide in advanced and/or metastatic pretreated soft tissue sarcomas

Background: Ifosfamide has important activity in pretreated soft tissue sarcomas (STS), and recent data support a clinically significant dose-response relationship for this agent. Administration by continuous infusion and hematopoietic support have rendered dose intensification regimens possible by reducing both hematologic and non-hematologic toxicities. The optimal dose and schedule of ifosfamide when given at high doses remain to be defined. In a previous phase I study, we demonstrated the feasibility of a continuous infusion (c.i.) high-dose ifosfamide (HDI) regimen in the ambulatory setting for patients with advanced solid tumors. The objective of the present phase II study was to assess the antitumor activity and toxicity of such a schedule in patients with advanced pretreated STS.Patients and methods: Thirty-eight patients with advanced and/or metastatic STS, all pretreated with an anthracycline with or without standard-dose ifosfamide, were treated. Ifosfamide was given by c.i. at a dose of 3.5 g/m²/day over four consecutive days, with equidose mesna uroprotection over five days. G-CSF was added at a dose of 200 µg/m²/day subcutaneously from day 6 to day 12. Cycles were repeated every three weeks in the outpatient setting.Results: A total of 159 cycles of therapy were given (median 4 per patient, range 3–6). Treatment compliance was generally satisfactory. The major toxicity was hematologic, with six febrile neutropenic episodes requiring hospitalisation and parenteral antibiotics. Acute renal failure occurred in one patient after three cycles of therapy; central nervous system toxicity was mild. An overall response rate of 39% was observed (95% confidence interval, 26% to 55%), with one complete and 14 partial remissions. All but one of the responder patients had previously received standard-dose ifosfamide. The median response duration was nine months (range 5–21+ months), and the overall median survival ranged from 6–30+ months (median 13 months).Conclusions: High-dose ifosfamide is an active regimen in anthracycline- pretreated STS. Future clinical trials should be aimed at evaluating the impact of different administration schedules on clinical response and outcome. The potential role of HDI as front-line chemotherapy as well as in the adjuvant treatment of STS needs to be investigated in randomized trials.