Evaluation of cyclophosphamide dosage schedules in breast cancer.

Dosage recommendations for cyclophosphamide therapy are examined in the light of an accumulated experience that this agent provides a useful palliation in 25% to 35% of patients with advanced breast cancer. It is concluded that an attempt to press dosage to the extreme limits of marrow tolerance does not significantly increase the likelihood of obtaining palliation, while posing a danger to the patient's life.It is also concluded that continuous low dosage schedules appear to achieve a similar incidence of tumour palliation to that from intermittent high dosage of cyclophosphamide. The latter schedule has the disadvantage of a considerably higher incidence of side effects, such as loss of scalp hair, nausea, cystitis and haemopoietic damage. Intensive dosage may however be more efficacious in the occasional case involving urgent management of a localized rapidly growing tumour. Consideration is given to other factors which may affect the degree and duration of palliation by cyclophosphamide, and to measures claimed to decrease the degree of toxicity.