MM-069: Autologous Hematopoietic Stem Cell Transplant in Multiple Myeloma: Plerixafor Mobilization and Progression-Free Survival

Abstract

Context: Plerixafor is a CXCR4 receptor antagonist developed for improving the mobilization of CD34+ cells prior to collection for autologous hematopoietic stem cell transplantation (Auto-HSCT) in hematologic malignancies, used when a high rate of insufficient collection by apheresis is expected. In multiple myeloma (MM), apart from an increase in the number of CD34+ cells, it has been shown a rise in the amount of plasma cells collected. Objective: Our hypothesis is that Plerixafor-mobilized patients and their potentially contaminated product could have an impact on their relapse-free survival. The primary outcome of this study was to evaluate if the addition of Plerixafor to filgrastim (G-CSF+P) for mobilization phase was related to a lower progression-free survival (PFS) compared to patients who received only filgrastim (G-CSF). Design: Observational, retrospective, longitudinal trial that included adults with MM who received Auto-HSCT between January 2012 to May 2019. Mean follow-up for surviving patients was 37 months. Setting: Hospital care, high-complexity center. Patients or other participants: 88 MM patients received Auto-HSCT in the studied period. 28 were excluded due to insufficient follow-up, second transplant, or missing relevant data. Median age was 57 years (range 31-73). A mean of 4.67 (± 2.42) and 6.65 (± 3.17) × 106 CD34+ cells/kg were infused in the G-CSF and G-CSF+P groups, respectively. Interventions: Follow-up after Auto-HSCT. Main outcome measures: Kaplan-Meier analysis to determine PFS and overall survival (OS). Results: Median PFS (n=60) was 24 months. In the subgroup analysis, PFS was 36.3 months for the filgrastim group (n=25) and 21.5 months for patients who received G-CSF+P (n=35; p=0.24). Median OS was 70 months (70 months vs not reached for G-CSF and G-CSF+P groups, respectively, p=0.6). Conclusions: Adding Plerixafor prior to autologous collection in MM showed a tendency towards a lower PFS, and a controlled trial with a larger sample size and longer follow-up is needed to define if this trend becomes statistically significant. Biological studies, such as the quantification of plasma cells and their apoptotic rate could add to the evaluation of the impact of the mobilized product in the relapse rate of MM patients.