Comparison Between Pegfilgrastim and Filgrastim-Based Autologous Hematopoietic Stem Cell Mobilization in the Setting of Patient Adapted (“Just in Time”) Plerixafor: Efficacy and Cost Analysis

Autologous hematopoietic stem cell (AHSC) mobilization is often performed utilizing filgrastim (G-CSF) without prior chemotherapy. The CXCR4 inhibitor plerixafor enhances the ability of filgrastim to mobilize CD34+ cells but adds substantial cost to the mobilization. Several algorithms have been proposed utilizing the patient's actual capacity to mobilize CD34+ cells to determine the need to add plerixafor after filgrastim has been initiated. The pegylated form of filgrastim (pegfilgrastim) has been used as an alternative and more convenient method of mobilization and has in a few instances been utilized with plerixafor. We hypothesize that replacing weight-based filgrastim with flat dose pegfilgrastim in a validated cost-saving mobilization algorithm for patient-adapted use of plerixafor will add convenience without increase in cost.

Single center retrospective analysis comparing mobilization outcomes and estimated total cost of mobilization in two consecutive cohorts undergoing filgrastim mobilization (FIL) or pegfilgrastim mobilization (PEG) prior to AHSCT for multiple myeloma (MM) or lymphoma (LY). Subjects in FIL received filgrastim 10 mcg/kg/day subcutaneously continuing until completion of collection while subjects in PEG received one flat dose of 12 mg of pegfilgrastim. In both cohorts peripheral blood CD34+ cells (PB-CD34+) enumeration was performed on the fourth day after initiation of growth factor. Subjects surpassing a certain target-specific threshold of PB-CD34+ (e.g 14 cells/mm³ for target of 3 × 10⁶ CD34+/kg and 25 cells/mm³ for target of 6 × 10⁶ CD34+/kg) started apheresis on the same day while subjects with lower PB-CD34+ received plerixafor 240 mcg/kg subcutaneously in the evening of the fourth day and apheresis was started on the fifth day (Figure 1). Decision to use of plerixafor followed the same previously validated algorithm in both cohorts. Apheresis, and growth factor +/− plerixafor were continued until the mobilization target was met. Analysis of estimated total cost of mobilization utilized average wholesale price (AWP) for drugs and institutional average charges for apheresis, cryopreservation and laboratory tests from a representative sample of subjects.

Seventy-four consecutive subjects were included in FIL and 47 in PEG. The two cohorts were comparable in terms of age (57.5 vs. 52.2), proportion of patients with diagnosis of MM (63.5% vs.66%), proportion of MM patients previously exposed to lenalidomide (63.8% vs. 51.6%), average body weight (82.9 vs.84 kg) and average mobilization target (4.5 vs. 5 × 10⁶ CD34+/kg). Overall 68/74 in FIL and 43/47 patients in PEG met the mobilization target (Table). Only one patient in each cohort required re-mobilization before proceeding to AHSCT. Median PB-CD34+ on day 4 was significantly higher in PEG. Consequently, by utilizing the same decision algorithm, patients in PEG received fewer subcutaneous injections and were less likely to require administration of plerixafor. Cohorts had near identical average number of apheresis sessions and comparable CD34+ yield. The estimated cost associated with growth factor was on average US$3,069 higher in PEG, but it was counterbalanced by an estimated $4,287 saving in plerixafor cost, resulting in no significant difference in the estimated overall cost of mobilization.

Single administration of pegfilgrastim 12 mg is associated with better CD34+ mobilization than filgrastim 10 mcg/kg/day in patients with MM and LY allowing for effective mobilization with less frequent use of plerixafor. Pegfilgrastin with patient adapted used of plerixafor is a reliable, convenient and cost-neutral strategy for AHSC mobilization.

Costa:Genzyme: Honoraria. Off Label Use: Pegfilgrastim - autologous hematopoietic stem cell mobilization.