SOLID TUMOR-MODELS FOR THE ASSESSMENT OF DIFFERENT TREATMENT MODALITIES .14. EVALUATION OF HOST AND TUMOR RESPONSE TO CYCLOPHOSPHAMIDE AND RADIATION

The effect of increasing doses of cyclophosphamide (50-250 mg/kg) on the time of occurrence of maximal and minimal tumor growth rates, tumor volume reduction, and linear doubling times (LDT) on the solid tumor model H-4-II-E have been determined. Tumor response to cyclophosphamide was classified as class I, tumor regression; class II, pseudo-regression; and class III, slow-down. The overall treatment efficiency (OTE) has been used to assess the magnitude of tumor volume changes after treatment. The maximum OTE occurred after 150 mg/kg of cyclophosphamide. Increasing the dose to 200 and 250 mg/kg of cyclophosphamide resulted in a decrease in OTE. Similar parameters were utilized to measure the effectiveness of increasing doses of local tumor radiation (750, 1500, 2000, 2500, 3000 and 3500R). The major increase in OTE occurs when the radiation dose is increased from 750R to 2000R. Increasing the dose further to 3500R results in smaller incremental increases in the OTE. Results of the study indicate that increasing the cyclophosphamide dose beyond a certain level (i.e. 150 mg/kg) increases mortality and morbidity without concomitant therapeutic benefit. The effects of increasing the dose of local tumor radiation on life span have given results which suggest that increasing the total radiation dose beyond a certain limit is less effective in increasing life span. © 1979.