Plerixafor is effective given either preemptively or as a rescue strategy in poor stem cell mobilizing patients with multiple myeloma.

Background: Harvest of more than one CD34+ stem cell transplant has become the standard, to ensure the option for a second autologous transplantation in patients with relapsed or progressive multiple myeloma (MM). Additional administration of the CXCR-4 inhibitor plerixafor has been shown to increase the efficiency of CD34+ stem cell harvest. However, the algorithm when to apply plerixafor is still under debate.

Study Design And Methods: In this retrospective study, 46 MM patients were categorized into four groups according to their CD34+ stem cell count in peripheral blood (PB) and mobilization with or without plerixafor: Group A comprised poor mobilizers with CD34+ cell counts of fewer than 20 × 10(6) /L in PB. Group B included inadequate mobilizers with CD34+ cell counts of 20 × 10(6) /L or more in PB and a low CD34+ stem cell yield in the first leukapheresis session. Patients receiving plerixafor preemptively (Group A1) and as a rescue strategy (Group B1) were compared to patients continuing stem cell collection with granulocyte-colony-stimulating factor alone (Groups A2 and B2).

Results: In both, the preemptive and the rescue settings, plerixafor enhanced the CD34+ stem cell yield significantly. Poor mobilization and administration of plerixafor was not associated with delayed engraftment.

Conclusion: Our data demonstrate that administration of plerixafor is safe and effective and facilitates a significantly higher CD34+ stem cell harvest. Based on the presented data, we propose an algorithm for the use of plerixafor for CD34+ stem cell mobilization and harvesting in poor mobilizing myeloma patients.