A randomized phase 3 study of peripheral blood progenitor cell mobilization with stem cell factor and Filgrastim in high-risk breast cancer patients

This randomized study compared the number of leukaphereses required to collect an optimal target yield of 5 x 10⁶ CD34⁺ peripheral blood progenitor cells/kg, using either stem cell factor (SCF) at 20 μg/kg/d in combination with Filgrastim at 10 μg/kg/d or Filgrastim alone at 10 μg/kg/d, from 203 patients with high-risk stage II, III, or IV breast cancer. Leukapheresis began on day 5 of cytokine administration and continued daily until the target yield of CD34⁺ cells had been reached or a maximum of 5 leukaphereses performed. By day 5 of leukapheresis, 63% of the patients treated with SCF plus Filgrastim (n = 100) compared with 47% of those receiving Filgrastim alone (n = 103) reached the CD34⁺ cell target yield. There was a clinically and statistically significant reduction (P < .05) in the number of leukaphereses required to reach the target yield for the patients receiving SCF plus Filgrastim (median, 4 leukaphereses) compared with patients receiving Filgrastim alone (median, 6 or more leukaphereses; ie, <50% of patients reached the target in 5 leukaphereses). All patients receiving SCF were premedicated with antihistamines, albuterol, and pseudoephedrine. Treatment was safe, generally well tolerated, and not associated with life-threatening or fatal toxicity. In conclusion, SCF plus Filgrastim is a more effective peripheral blood progenitor cell (PBPC)- mobilization regimen than Filgrastim alone. In addition to the potential for reduced leukapheresis-related morbidity and costs, SCF offers additional options for obtaining cells for further graft manipulation.