Favorable factors in the adjuvant therapy of breast cancer.

One hundred seventy-one patients received one year of melphalan or intermittent cyclophosphamide, methotrexate, and fluorouracil after mastectomy for breast cancer with involved axillary nodes. Analysis with a median follow-up of three years indicates a favorable outcome only for patients with 1-3 positive nodes who were treated with melphalan and who experienced a leukocyte count less than 3,000/mm3 (3.0 X 10(9)/l). Tumor size, average percentage of dose received, menopausal status, and type of chemotherapy were not significant factors in recurrence of disease, after adjustment for the number of positive nodes and leukocyte count nadir during treatment based on a multifactorial analysis. These data suggest that administration of a dose of melphalan which does not produce a leukocyte count of less than 3,000/mm3 is ineffective in preventing early recurrence of disease. Since oral melphalan is known to be erratically absorbed, lack of hematologic toxicity may well be due to variable absorption of the drug on a fixed-dose region. Failure to prevent recurrence of disease in this and other trials using oral melphalan may be due to chemotherapy-related as well as disease-related factors.