The purpose of this study was to determine the maximum tolerated dose (MTD) of infusional gemcitabine given in conjunction with intravenous (I.V.) cyclophosphamide, and to determine whether the regimen produced a response rate of at least 40% in patients with metastatic breast cancer who have been previously treated with taxanes. Patients received cyclophosphamide (600 mg/m2) I.V. followed immediately by gemcitabine (100, 150, or 200 mg/m2) given as a 24-hour infusion (every 3 weeks) using an accelerated dose-escalation schema. Dose-limiting toxicity was defined as a neutrophil nadir < 500/μL, platelet nadir < 50,000/μL, or ≥ grade 2 nonhematologic toxicity (≥ grade 3 toxicity during the standard dose-escalation portion of the study). Twelve patients received a total of 32 cycles of therapy. The MTD of gemcitabine was 150 mg/m2. Dose-limiting toxicities at 200 mg/m2 included neutropenia and mucositis. One patient with lymphangitic lung metastases had a partial response (8%; 95% confidence intervals: 0%, 23%). This patient developed grade 4 transaminase and total bilirubin elevation that occurred affer the sixth cycle of therapy. The study was terminated due to an insufficient number of responses. The MTD of gemcitabine given as a 24-hour infusion is 150 mg/m2 when used in conjunction with cyclophosphamide (600 mg/m2) every 3 weeks. This regimen is not likely to produce more than a 40% response rate in patients with metastatic breast cancer previously treated with taxanes.
- Dose-limiting toxicity
- Maximum tolerated dose