Oral alkylating agents for breast cancer therapy.

Oral cyclophosphamide is well tolerated and effective. Published data support its use as part of adjuvant and metastatic breast cancer treatment regimens. Cyclophosphamide has generally been administered at a higher dose intensity when given orally compared with intravenous infusion. However, there is currently no evidence that oral cyclophosphamide is either more toxic or more or less effective than an equivalent dose of intravenous cyclophosphamide. There is evidence in both the adjuvant and metastatic settings that classical oral cyclophosphamide-methotrexate-fluorouracil (CMF) is more effective than intravenous CMF, possibly because of the greater dose intensity of classical CMF. Prolonged administration of oral cyclophosphamide up to high cumulative doses is associated with an elevated risk of a secondary leukaemia. The rates of chemotherapy-related amenorrhoea with oral cyclophosphamide are directly related to the total dose of cyclophosphamide administered and the patient's age. With the growing availability of other oral cytotoxic agents with demonstrated effectiveness in breast cancer, it is likely that oral cyclophosphamide will be incorporated once again into regimens for both metastatic and adjuvant treatment.