Beyond CD34+ cell dose: impact of method of peripheral blood hematopoietic stem cell mobilization (granulocyte-colony-stimulating factor [G-CSF], G-CSF plus plerixafor, or cyclophosphamide G-CSF/granulocyte-macrophage [GM]-CSF) on number of colony-forming unit-GM, engraftment, and Day +100 hematopoietic graft function.

BACKGROUND: The dose of CD34+ cells/kg in the mobilized peripheral blood product is the main determinant of neutrophil and platelet (PLT) engraftment after autologous hematopoietic stem cell transplantation (AHSCT). Whether the method of mobilization, namely, granulocyte-colony-stimulating factor (G-CSF) alone (G), G-CSF plus plerixafor (G+P), or cyclophosphamide + G/granulocyte-macrophage (GM)-CSF (Cy+G/GM), independently affects number of colony-forming unit (CFU)-GM, engraftment, and hematopoietic graft function is unknown.

STUDY DESIGN AND METHODS: We used a database of AHSCT patients with multiple myeloma or lymphoma to identify three groups with different mobilization strategies receiving transplantation with similar CD34+ cell doses. Groups were compared in terms of CFU-GM, ratio of CFU-GM/CD34+, engraftment of neutrophils and PLTs, and hematopoietic graft function on Day +100.

RESULTS: Ninety-six patients were included in the analysis, 26 G, 32 G+P, and 38 Cy+G/GM, with median cell doses of 4.21 × 10(6) , 4.11 × 10(6) , and 4.67 × 10(6) CD34+/kg, respectively (p = 0.433). There was no significant difference in number of CFU-GM between the three groups; however, the ratio of CFU-GM/CD34+ was significantly lower for G+P (p = 0.008). Median time for neutrophil engraftment was 13 days in G+P and 12 days in G and Cy+G/GM (p = 0.028), while PLT engraftment happened at a median of 14.5 days in G+P versus 12 days in G and 11 days in Cy+G/GM (p = 0.012). There was no difference in hematopoietic graft function at Day +100.

CONCLUSION: Plerixafor-based mobilization is associated with slightly reduced number of CFU-GM and minimal delay in engraftment that is independent of CD34+ cell dose. Hematopoietic graft function on Day 100 is not affected by mobilization strategy.