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？×？106 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？×？106 vs. 10.4？×？106/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