Optimization of Plerixafor Utilization Based on Peripheral Blood CD34+ Count for Autologous Peripheral Blood Stem-Cell Collection

Introduction: Peripheral CD34+ cells may be mobilized using filgrastim (G-CSF) alone or in combination with chemotherapy. However, some patients also require plerixafor, an inhibitor of C-X-C chemokine receptor type-4, for adequate mobilization. Given its cost, judicious utilization of plerixafor is warranted.

Material and Methods: A retrospective analysis of autologous stem-cell mobilization was performed at a tertiary-care medical center in adult patients with multiple myeloma and lymphoma; here we will focus on the utility of repeat plerixafor dosing. Patients were mobilized at the treating physician's discretion with filgrastim plus plerixafor or chemotherapy plus filgrastim plus plerixafor. Collections were initiated once peripheral CD34+ counts reached 20/µL (or 10/µL if chemotherapy mobilized); plerixafor was administered if these counts were not reached after 4 or 8 days, respectively, of filgrastim treatment.

Results: Patients with multiple myeloma (86) or lymphoma (30) were evaluated. One hundred five were mobilized by filgrastim plus plerixafor and 11 by chemotherapy plus filgrastim plus plerixafor. No patient that received plerixafor with a CD34+ count <5/µL after chemotherapy mobilized the next day. The end collection goal was achieved in 86 (81.9%) of the filgrastim plus plerixafor group and 7 (63.6%) of the chemotherapy plus filgrastim plus plerixafor group. Patients given at least one dose of plerixafor were divided into groups based on collection goal, peripheral blood CD34+ cell count after 1 dose and the first day collection yield: Group 1) Goal of 3x10^6/kg and CD34+ count ≥ 30 cell/µL vs < 30 cell/µL; Group 2) Goal of 6x10^6/kg and ≥ 50% of collection goal after 1 day of collection vs CD34+ count < 50 cell/µL or < 50% of collection goal. Forty of 42 (95%) patients in Group 1 with a CD34+ count ≥ 30 cell/µL achieved their end collection goal after one plerixafor dose. Eighteen of 19 (95%) patients in Group 1 with a CD34+ count <30 cell/µL received a second dose of plerixafor and 8 (44.4%) achieved their end collection goal. Twenty-eight of 32 (87.5%) patients in Group 2 with ≥ 50% of collection goal achieved on the first day of collection reached their end collection goal after one plerixafor dose. Nine of 12 (75%) patients in Group 2 with a CD34+ count of < 50 cells/µL or <50% collection goal received an additional dose of plerixafor and 6 (66.7%) achieved their end collection goal.

Conclusion: Based on these data, we have developed the following repeat plerixafor dosing algorithm: 1) for a collection goal is 3x10^6/kg, administer a second dose of plerixafor if the CD34+ count on the first day of collection is < 30 cell/µL, and 2) for a collection goal of 6x10^6/kg, administer a second dose of plerixafor if the CD34+ count on the first day of collection is < 50 cell/µL or if the first day of collection yields <50% of the end goal. This algorithm optimizes pharmacy, apheresis and stem cell processing resources.