Cytarabine + G-CSF is more effective than cyclophosphamide + G-CSF as a stem cell mobilization regimen in multiple myeloma.

Cyclophosphamide (Cy) plus granulocyte-colony stimulating factor (G-CSF) is currently a standard regimen for hematopoietic stem cell (HSC) mobilization in patients with multiple myeloma (MM). However, cytarabine (AraC) in intermediate doses plus G-CSF seems to have a higher mobilization efficacy. The aim of this study was to retrospectively compare mobilization using AraC and Cy. Thirty consecutive MM patients were mobilized by Cy + G-CSF, and the subsequent 40 patients by AraC + G-CSF. Both groups were comparable. The target yield of 10 × 10 CD34+ cells/kg (for tandem and 2 additional transplantations) was achieved in 98% (AraC) and 57% (Cy) of patients (p < 0.0001) by 1.2 and 2.1 apheresis (means), and by single apheresis in 83 and 17% of patients, respectively. AraC mobilization resulted in higher peak concentration of CD34+ cells in blood (median 238.0 vs. 87.9/µL, p < 0.0001) and higher CD34+ yield (median 28.6 × 10 vs. 10.4 × 10/kg, p < 0.0001) compared to Cy mobilization. Toxicities were comparable except for thrombocytopenia gr. 4, observed in 50% of patients after AraC (Cy 7%). In view of these results, we conclude that mobilization with AraC plus G-CSF is very effective with acceptable toxicity and could be considered in MM patients with planned or expected higher numbers of transplantations.