Effect of the rhythm of cyclophosphamide administration on its antitumor action and the immune response of mice with methylcholanthrene sarcoma.

The therapeutic effect of cyclophosphamide (CP) in relation to the dose and rhythum of its administration was studied in C57BL/6 mice with a methycholanthrene-induced sarcoma. The optimal scheme giving a complete cure of the experimental animals was 5 injections, each of 199 mg/kg CP at intervals of 10 days. The effect of the total dose of CP on humoral antitumor immunity was demonstrated: after injection of 100 mg/kg CP the animals' serum lost its ability to stimulate tumor growth and acquired cytotoxic properties. The serum of animals receiving the total doses of CP above 400 mg/kg lost its effect on tumor growth. The doses of CP used did not affect cellular antitumor immunity (the cytotoxicity of the lymphocytes and resistance of the tumor to retransplantation.).