Effect of cyclophosphamide on development of reticulum cell sarcoma in SJL/J mice.

Studies to determine the effect of cyclophosphamide (CY) on the development of reticulum cell sarcoma (RCS) in SJL/J mice indicated a dependence on the duration of the test period. Age also appeared a factor of importance. Thus, a comparison of tumor incidences at 52 weeks of age showed maximal inhibition when CY was administered at 40 weeks, minimal inhibition when the drug was given at 30 weeks, and intermediate inhibition when treatment was initiated at 10 and 20 weeks. Consistent with these findings, long-term treatment of 40-week-old SJL/J mice with low doses of CY resulted in an increase in the mean survival time and in a reduction in the incidence of RCS.