Sixteen-week dose-intense chemotherapy in the adjuvant treatment of breast cancer.

Fifty-three women with breast cancer were treated with a new 16-week dose-intense, chemotherapy regimen. Patients with operable breast cancer with 10 or more histologically positive axillary nodes were treated with this five-drug regimen that incorporated the concepts of weekly chemotherapy, sequential administration of antimetabolites, and continuous infusion of fluorouracil (5-FU). The chemotherapy regimen consisted of eight cycles (each of 2 wk duration) of 100 mg of cyclophosphamide/m2 orally on days 1-7, 40 mg of doxorubicin/m2 intravenous (IV) on day 1, 100 mg of methotrexate/m2 IV on day 1 with 10 mg of leucovorin rescue/m2 every 6 hours for six oral doses on day 2, 1 mg of vincristine IV on day 1, and 600 mg of 5-FU/m2 IV at hour 20 over 2 hours. A continuous infusion of 300 mg of 5-FU/m2 per day was given IV on days 8-9 of each 2-week cycle. The doses and schedule of drug administration were designed to minimize dosage reduction and treatment delay. At a median follow-up of 17 months, there have been eight relapses in the 53 patients. The actuarial 3-year disease-free survival is 80% (95% confidence interval, 62% to 90%). The major side effects were attributable to myelosuppression. Absolute neutrophil counts less than 250/microL were noted in 12 (23%) patients; seven patients (13%) required hospitalization for management of neutropenic fever. No treatment-related deaths occurred. Ninety-four percent of the planned doses were administered, and only 5% of the courses were delayed because of toxic reactions. The encouraging therapeutic data, manageable side effects, and our ability to deliver over 90% of the planned doses provide the rationale for a phase III comparison of this new dose-intense regimen and standard chemotherapy in patients with operable disease and positive axillary nodes.