Phase 1/2 study of intravenous paclitaxel and oral cyclophosphamide in pretreated metastatic urothelial bladder cancer patients

Abstract

To the authors' knowledge, no previous studies have been reported with the combination of paclitaxel and oral cyclophosphamide in patients with metastatic bladder cancer. A phase 1/2 study was conducted of paclitaxel in combination with oral cyclophosphamide for patients with advanced urothelial bladder cancer who had been previously treated with gemcitabine/cisplatin chemotherapy as first-line metastatic treatment. This was a single-arm phase 1/2 study. Patients were treated with paclitaxel and oral cyclophosphamide at 3-week intervals until disease progression or irreversible toxicity occurred. Primary endpoints were to determine the maximum tolerated doses (MTD) and objective response rate; secondary endpoints were safety, time to disease progression (TTP), and overall survival (OS). Forty-four patients were enrolled. Dose levels of paclitaxel of 175 mg/m(2) (Day 1) and cyclophosphamide of 50 mg (Days 1-7 orally) (dose level I) of a 21-day cycle were tolerated without dose-limiting toxicities (DLTs). At a cyclophosphamide dose of 100 mg (dose level II) the MTD was exceeded; 3 of 6 patients experienced a DLT (grade 3 constipation and grade 4 neutropenia and thrombocytopenia [toxicities were graded using National Cancer Institute Common Toxicity Criteria (version 3.0)]). Dose level I was expanded and determined to be the MTD. A total of 32 patients were treated at dose level I in the phase 2 portion. Partial responses were observed in 31% of patients (10 of 32 patients; 95% confidence interval [95% CI], 17%-45%). Grade 1/2 vomiting, peripheral neuropathy, and neutropenia were the most common side effects, noted in 11 (34%), 8 (25%), and 10 (31%) patients, respectively. The median TTP was 5 months (95% CI, 2 months-7.5 months) and the median OS was 8 months (95% CI, 4 months-14 months). The combination of paclitaxel and cyclophosphamide is well tolerated and associated with promising efficacy. Further trials are needed to confirm these preliminary results.