Changes in peripheral blood composition following single and repeated courses of intermittent cancer chemotherapy

In fifteen patients treated for lung cancer with a combination of vincristine (VCR) (2 x 0.325 mg/kg), amethopterin (MTX) (3 x 0.4 mg/kg) and cyclophosphamide (CY) (30-50 mg/kg) at monthly intervals the peripheral blood parameters were determined every 2-4 days. The values of these parameters including neutrophils, lymphocytes, platelets, erythrocytes and reticulocytes decreased uniformly reaching the lowest level about the 11th day post each course of chemotherapy. Subsequently, by the 17th day, the values of all these parameters except the red cell count returned to the pretreatment levels. The only parameter whose nadir value was associated with known risk to the health was the absolute neutrophil count. The period of dangerous decrease of this count began on the 6th day and ended approximately on the 17th day after cyclophosphamide infusion. Repeated courses had no additive toxicity since the time interval between courses allowed for hematopoietic recovery. However, the gradual decrease in the red cell count was observed during intermittent chemotherapy.