Feasibility of dose-intensive continuous 5-fluorouracil, doxorubicin, and cyclophosphamide as adjuvant therapy for breast cancer.

BACKGROUND: Several studies support the belief that the efficacy of adjuvant chemotherapy in breast cancer is related to the dose intensity of the chemotherapy used (expressed in milligrams per square meter per week). Retrospective analyses indicate that the actual delivered dose intensity may correlate more strongly with efficacy than the intended dose delivery.
METHODS: A doxorubicin-based adjuvant regimen was studied for breast cancer. It was modeled on the Southwest Oncology Group's regimen of cyclophosphamide, methotrexate, and 5-fluorouracil in that daily oral cyclophosphamide and weekly intravenous 5-fluorouracil were used, but weekly doxorubicin was substituted for methotrexate and administered in both the adjuvant and neoadjuvant setting to 29 patients.
RESULTS: The actual dose delivery was 1.21-1.24-fold that calculated for the delivered dose in the two other adjuvant regimens using the same three drugs (5-fluorouracil, doxorubicin, and cyclophosphamide) for which this could be determined. This regimen was tolerated well. Toxicity was minimal and consisted largely of expected neutropenia.
CONCLUSIONS: Whether improved dose intensity can be increased further with the use of growth factors or actually confers improved outcomes awaits the results of larger future trials.