Peripheral Blood Stem Cell Mobilization for Autologous Hematopoietic Stem Cell Transplantation in Multiple Myeloma: Growth Factors Only Vs. Growth Factors + Chemotherapy

Abstract

<h3>Background</h3> Strategies for mobilization and collection of peripheral blood stem cells (PBSC) for autologous hematopoietic stem cell transplant (auto-HCT) include growth factors (GF) such as filgrastim, either alone or with chemokine receptor antagonist plerixafor, or filgrastim/plerixafor in combination with chemotherapy (GF + chemo). <h3>Methods</h3> In this single center retrospective analysis, we compared PBSC mobilization with GF only (filgrastim +/- plerixafor) to GF + chemo. Chemotherapy used was cyclophosphamide alone, or modified CVAD. Primary endpoints were engraftment, transfusion requirement, duration of hospitalization, NRM, PFS and OS. <h3>Results</h3> We identified 1361 patients who had auto-HCT between 1988 and 2015; 1137 with GF only and 224 with GF + chemo. As shown in Table 1, more patients in the GF + chemo group had high-risk cytogenetics (25.6 vs 20.3%), lower ≥VGPR rate to induction (20 vs 50%), and required more intense conditioning (25 vs 13%). Additionally, patients with GF + chemo collected target PBSC in fewer days (2 vs. 3), received a higher CD34+ cell dose (5.6 vs. 4.1) with no difference in neutrophil or platelet engraftment, had longer hospitalization post auto-HCT (19 vs 17 days), and required more PRBC transfusions (2 vs 1), Table 2. The 100-day NRM was <1% in both groups (p=0.712). With a median follow up of 75.3 months, both PFS (HR=1.44 CI:1.22-1.69, p<0.001) and OS (HR=1.30 CI: 1.06-1.60, p=0.013) were significantly shorter in GF + chemo group. On multivariable Cox analysis, GF + chemo, older age, ISS stage III, high-risk cytogenetics and progressive disease after induction were associated with shorter PFS. <h3>Conclusion</h3> There was no statistically significant difference between GF only or GF + chemo in engraftment or NRM. The shorter survival in the GF + chemo group may be attributed to a higher proportion of poor-risk patients in that group.