Purpose: To evaluate the effect of filgrastim (recombinant human G-CSF) on radiation-induced neutropenia in a well defined, homogenous patient population.
Methods and materials: Seven patients who were to receive large field subdiaphragmatic irradiation after thoracic "mantle" fields for treatment of Hodgkin's disease entered this study. They received daily subcutaneous (SC) injections of filgrastim during subdiaphragmatic irradiation. Total white blood cell (WBC) and absolute neutrophil cell (ANC) counts were measured and compared to a historical series of patients, and hematological toxicity was assessed. The endpoints of the study were nadir WBC and ANC counts and time to WBC and ANC recovery.
Results: Compared to the historical series, filgrastim significantly increased the WBC and ANC throughout the period of subdiaphragmatic irradiation. Nadir WBC (5.98 +/- 1.24/mm3) and ANC (4.71 +/- 1.07/mm3) in the Filgrastim group were approximately two times those of the historical series (3.32 +/- 1.06/mm3 and 2.39 +/- 0.97/mm3 respectively; p < 0.002). Nadir platelet counts were not affected by filgrastim therapy. Three of seven patients reported mild musculoskeletal pain, but there was no other apparent toxicity.
Conclusion: Compared to the historical series, filgrastim therapy significantly increased WBC and ANC during extended field radiation therapy and was well tolerated. It may be clinically useful in other groups of patients who are likely to develop profound neutropenia during large field irradiation.