Mobilization and harvesting of peripheral blood stem cells: randomized evaluations of different doses of filgrastim

The effects of different doses of filgrastim on yields of CD34⁺ peripheral blood stem cells were evaluated in patients with breast cancer. 55 were randomized to receive filgrastim 10, 20, 30 or 40 μg/kg/d with more CD34⁺ cells/kg/apheresis harvested after the three highest dose levels. 35 additional patients were randomized to receive 10 or 30 μg/kg. The median number of CD34⁺ cells collected after 10 μg/kg (n= 31) was 0.7 × 10⁶/kg/apheresis (range 0.1–4.4) as compared to 1.2 (range 0.1–6.8) after 30 μg/kg (n= 32) (P= 0.04). Among patients randomized to 10 v 30 μg/kg, more (50%) achieved 5.0 × 10⁶ CD34⁺ cells/kg and less aphereses were required to achieve 2.5 × 10⁶ CD34⁺ cells/kg after the higher dose (P= 0.04). In multivariate analyses, patients receiving 10 μg/kg (n= 31) had lower yields of CD34⁺ cells (P= 0.026) and had a 3.3-fold increase in the probability of not achieving 5.0 × 10⁶ CD34⁺ cells/kg as compared to patients receiving 20–40 μg/kg (n= 59). Patients who had received radiation had a 2.9-fold probability of not achieving 2.5 × 10⁶ CD34⁺ cells/kg. These data suggest that, in patients with good marrow reserves, doses of filgrastim > 10 μg/kg/d mobilized more CD34⁺ cells and may be useful when high numbers of CD34⁺ cells are desired.