Short-term administration of granulocyte-macrophage colony stimulating factor decreases hematopoietic toxicity of cytostatic drugs.

Background: Administration of granulocyte-macrophage colony stimulating factor (GM-CSF) is followed by a rapid increase in the proliferative activity of the hematopoietic precursors. Within 72 hours after its suspension, however, establishment of a negative feedback results in a reduction of the proliferative activity of the hyperplastic marrow to values below the baseline, suggesting refractoriness of hematopoietic progenitors to the action of cell-cycle-specific cytostatic agents.

Methods: The hypothesis that short treatment with GM-CSF before chemotherapy could reduce the hematopoietic toxicity of cytostatics was investigated by administering GM-CSF glycosylate (Sandoz, Basel, Switzerland/Schering-Plough, Kenilworth, NJ) subcutaneously with a 5.5 micrograms/kg protein dosage per day from day-6-day-4 before each course of adjuvant chemotherapy (cyclophosphamide, epirubicin, 5-fluorouracil/cyclophosphamide, methotrexate, 5-fluorouracil alternate) in patients with node-positive breast cancer. Twelve patients were randomized to receive GM-CSF before chemotherapy or only at chemotherapy. The hematologic picture and dose intensity of chemotherapy were compared in the two groups of patients.

Results: In the group of patients receiving chemotherapy only, 22% of the cycles had to be postponed because of leukopenia, with a consequent reduction of the dose intensity, whereas in the GM-CSF group, the neutrophil counts remained at significantly (P < 0.001) higher levels, and there were no delays in chemotherapy administration. No substantial systemic toxicity was associated with this brief GM-CSF schedule. Moreover, GM-CSF treatment did not result in delayed depletion of the hematopoietic pool.

Conclusions: Short treatment with GM-CSF can enable the dose intensity of conventional protocols of proven efficacy to be increased.