Continuous-infusion 5-fluorouracil combined with doxorubicin and cyclophosphamide: feasibility study

Previous studies have demonstrated continuous-infusion 5-fluorouracil (CI 5-FU) to be an active single-agent treatment for breast cancer without significant myelotoxicity. These qualities made CI 5-FU an attractive agent for combination with other effective but myelosuppressive agents. In this study we attempted to determine the maximal doses of CI 5-FU that could be added to a combination of agents known to be dose limited by myelotoxicity, doxorubicin 50 mg/m2 day 2 and cyclophosphamide 150 mg/m2 days 3-12 of a 28-day cycle. Patients who received doxorubicin and cyclophosphamide alone developed significant myelotoxicity but did not develop stomatitis. The addition of 5-7 days of CI 5-FU at 200-300 mg/m2 was associated more closely with increased stomatitis (P = .11) than with increased granulocytopenia (P = .57). The stomatitis observed for low doses of CI 5-FU given with doxorubicin and cyclophosphamide would not have been expected for these low doses of CI 5-FU given as a single agent. We conclude that the addition of CI 5-FU to myelotoxic doses of doxorubicin and cyclophosphamide is not a promising therapeutic strategy for significantly increasing the effectiveness of this combination of agents.