Peripheral blood stem cell collection in multiple myeloma: A retrospective analysis of 6 years leukapheresis activity in 109 patients treated at the Istituto Nazionale dei Tumori of Milan

Double autologous stem cell transplantation is the standard treatment in newly diagnosed multiple myeloma (MM) patients younger than 65 years; therefore, optimization of leukapheresis is crucial. We performed a retrospective analysis of 297 leukaphereses comparing semiautomated (V4.7 in 20% of collections) versus automated (V6.0 in 80%) Caridian (COBE) Spectra versions and analyzing the influence of M-protein on the outcome. Both methods gave comparable collection efficiencies (CE%) (53.4% vs. 55.7% in V6.0 and V4.7, respectively) with similar leukapheresis time and processed volume. Harvest volume was higher in V4.7 (P <0.0001) with similar contamination of red blood cells (RBCs) (P = 0.77) and platelets (P = 0.09) when compared with V6.0. In patients with higher peripheral white blood cells (WBCs), V6.0 with adjusted harvest volume (+ CE% (P = 0.39) and better enrichment of nucleated cells (P <0.0,002) but higher RBCs (P <0.0,001) and platelets contamination (P = 0.001), when compared with a larger cycle volume in patients with lower WBCs. In hard to mobilize patients, CD34⁺ CE% was significantly more efficient with V4.7 than V6.0 (P <0.0,001). CD34⁺ CE% was unaffected by serologic M-protein, but platelet CE% was higher in the absence of M-protein (P = 0.0,003), without any reduction in peripheral patients platelets. We, therefore, conclude that in the setting of MM patients with a high WBCs count and/or low percentage of peripheral CD34⁺ cells, collections with V4.7 or adjusted cycle volume V6.0 gave comparable result in CD34⁺ CE%. RBCs and platelets contamination is higher if low cycle volume is chosen. In hard to mobilize patients, V4.7 is advisable.