Weekly paclitaxel and high-dose 5-fluorouracil plus leucovorin in hormone-refractory prostate cancer: In vitro combined effects and a Phase II trial

Purpose: Paclitaxel and 5-fluorouracil have been used to treat hormone-refractory prostate cancer with some success. In vitro data suggest that the combined cytotoxicity may be sequence dependent. Thus, we explored the combined effects of the 2 agents, both in vitro and in vivo. Patients and Methods: The combined cytotoxicity of paclitaxel and 5-fluorouracil, and the possible schedule dependence were studied in vitro using PC-3 and DU 145 cells and the microculture tetrazolium assay. There were 23 patients with hormone-refractory prostate cancer treated with the regimen T-HDFL: paclitaxel 90 mg/m(2) intravenously I hour on days I and 8; 5-fluorouracil 2000 mg/m2; and leucovorin 300 mg/m(2) intravenous 24-hour infusion on days 2 and 9, which repeated every 21 days. The allowed percentage of bone marrow irradiation was 50%. Results: Significant synergistic cytotoxicity was seen only when paclitaxel was given 24 hours before 5-fluorouracil. With the T-HDFL regimen, 11 (52%) of the 21 evaluable patients had >= 50% reduction of prostate-specific antigen, lasting for 6 weeks. Of the 7 patients with measurable disease, 2 had a partial response. Median overall survival was 14.1 months. Grade III/IV leukopenia occurred in 2 patients. There was no treatment-related death. Toxicities were well tolerated. Conclusions: The combined cytotoxicity of paclitaxel and 5-fluorouracil is schedule dependent. It is feasible to administer weekly paclitaxel and high-dose 5-fluorouracil infusions in patients with hormone-refractory prostate cancer. Our findings may serve as an important rationale for future trial design. (C) 2007 Elsevier Inc. All rights reserved.