Optimising parameters for peripheral blood leukapheresis after r-metHuG-CSF (filgrastim) and r-metHuSCF (ancestim) in patients with multiple myeloma: A temporal analysis of CD34⁺ absolute counts and subsets

Patients (n = 69) with multiple myeloma undergoing peripheral blood stem cell collection (PBSC) were treated with cyclophosphamide and a combination of recombinant methionyl human granulocyte colony-stimulating factor (r-metHuG-CSF, filgrastim) and recombinant methionyl human stem cell factor (r-metHuSCF, ancestim). The objectives of this study were to determine: (1) The proportion of patients reaching a target yield of ≥5 × 10⁶ CD34⁺ cells/kg in one or two successive large-volume (20 liter) leukapheresis procedures; (2) the optimal collection time for leukapheresis; (3) mobilization kinetics of CD34⁺ subsets in response to GCSF/SCF. All patients were mobilized with cyclophosphamide (2.5 g/m²) on day 0 followed by filgrastim (10 μg/kg ) plus ancestim (20 μg/kg) commencing day 1 and continuing to day 11 or 12. Of the 65 evaluable patients, 57 were considered not heavily pretreated and 96.5% obtained a target of ≥5 × 10⁶/kg in one collection. The median CD34⁺ cells/kg was 39.5 × 10⁶ (range: 5.2-221.2 × 10⁶). Subset analysis demonstrated the number of CD38^-, CD33^-, and CD133⁺ peaked at day 11; and CD34⁺, CD90⁺ cells peaked at day 10. The optimum day for leukapheresis was determined to be day 11. The median absolute peripheral blood CD34⁺ cell numbers on day 11 was 665 × 10⁶/l (range: 76-1481 × 10⁶/l). Eight of the 10 heavily pretreated patients were evaluable: three achieved the target dose in one leukapheresis (37.5%) and three (37.5%) achieved the target dose with two leukaphereses. Use of this mobilization strategy allowed the collection of high numbers of CD34⁺ cells and early progenitors and the ability to predictably schedule leukapheresis.