Reduced Lethality in Mice receiving a Combined Dose of Cyclophosphamide and Busulphan

Summary.-Animals treated with a sufficiently high dose of busulphan die about 14 days later from bone marrow failure. A single, appropriately timed injection of cyclophosphamide can save these mice. The nature of this protection is shown to be the cyclophosphamide induced elaboration of a humoral factor which stimulates haemopoietic recovery. THE USE of cytotoxic agents in cancer chemotherapy is often limited by the action of these agents on the normal, homoeostatic, proliferating cells of the body, particularly those of the bone marrow. Any substance which enhances haemopoietic recovery, particularly during bone marrow depression induced by cyto-toxic agents, is of importance. Cyclophosphamide, in addition t