Dose-finding study of paclitaxel and cyclophosphamide in women with advanced breast cancer.

The primary aim of this study was to define the maximum tolerated doses of paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) given by 3-hour infusion and cyclophosphamide given by intravenous bolus every 3 weeks in patients with breast cancer. Patients had received a maximum of one prior chemotherapy for advanced disease. The maximum tolerated dose of the combination was also determined with granulocyte colony-stimulating factor (G-CSF) support. The 80 women who took part in this study received 347 fully evaluable courses of therapy. Starting doses were paclitaxel 135 mg/m2 and cyclophosphamide 750 mg/m2; G-CSF support (5 microg/kg subcutaneously) was added at the subsequent cycle if specific dose-limiting toxicities had occurred during the previous cycle. Febrile neutropenia and severe thrombocytopenia defined the maximum tolerated doses as paclitaxel 200 mg/m2 and cyclophosphamide 2,000 mg/m2, with or without G-CSF support, in patients with or without a prior chemotherapy. Recommended doses were paclitaxel 200 mg/m2 and cyclophosphamide 1,750 mg/m2 in these two groups of patients. The overall response rate was 25% among patients who had received prior therapy for metastatic disease and 50% in patients who had not been previously treated. Complete remissions were reported in 9% of patients, but only among those who were previously untreated.