Abstract
Introduction: Filgrastim (FIL), administered as 4 or more daily multi-vial subcutaneous injections is the most commonly utilized growth factor for mobilization of autologous hematopoietic progenitor cells (auto-HPC) for transplantation. Plerixafor, a CXCR4 inhibitor, potentiates the effect of FIL by increasing the pool of circulating CD34+ cells and apheresis yield. Pegfilgrastim (PEG) is a long acting modification of FIL. Prior experience indicates that single fixed dose PEG can be utilized for auto-HPC mobilization with at least similar performance compared to daily, weight-based dose FIL, but cost is a concern.
Methods: We adopted a standardized mobilization protocol consisting of PEG 6 mg on day 1, plerixafor 240 mcg/kg on day 3 and collection of auto-HPC by apheresis on day 4. When CD34+ collection target (3 x 106 CD34+/kg for patients collecting for 1 transplant and 6 x 106 CD34+/kg for patients collecting for 2 transplants) was not met on the first day of collection, evening plerixafor administration followed by next-day collection was repeated until target met or a maximum of 3 collections. Auto-HPCs were collected by apheresis with processing of approximately 3 blood volumes utilizing Cobe® Spectra or AmicusTM machine. Mobilization failure was defined as a collection < 2 x 106 CD34+/kg, considered the minimum cell dose for one transplant procedure. We prospectively collected information on mobilization outcomes for 164 consecutive auto-HPC mobilizations. We compared the estimated cost of mobilization drugs with PEG vs. simulated cost with FIL or tbo-filgrastim (TBO) at dose of 10 mcg/kg/day administered for 4 days prior to first collection and daily until collection completion, with this regimen assumed to be of similar efficacy than PEG. Drug costs were estimated using average sales price (ASP): PEG $4,191.34/ 6mg, FIL $1.009/ 1mcg, TBO $0.665/ 1mcg, and plerixafor $312.10/ 1mg. Actual body weight was used for estimation of FIL and TBO dose.
Results: Among the 164 consecutive patients, 11 had the diagnosis of Hodgkin lymphoma, 20 non-Hodgkin lymphoma and 133 multiple myeloma or another plasma cell dyscrasia. Median age of patients was 60 years (range 21-73) and 92 (56%) were men. Median weight of patients was 84kg (range 51-175). Among the patients with a plasma cell dyscrasia, 87 (65%) had received prior lenalidomide, an agent known to impair HPC mobilization. Overall 4 patients (2.4%) had mobilization failure. One hundred and forty-two (87%) met the pre-established target while 18 (11%) collected enough CD34+ cells to proceed to transplant but fewer cells than pre-established target. The median CD34+/mm3 in peripheral blood on the first day of collection was 71 (range 2-481). The median collection yield on the first day was 6.06 x 106 CD34+/kg (range 0.34-39.60) and median total collection yield was 4.52 x 106 CD34+/kg (range 0.81-18.60) for patients with target of 3 x 106 CD34+/kg and 7.97 x 106 CD34+/kg (range 0.34-39.60) for patients with target of 6 x 106 CD34+/kg. Overall 77 (47%) patients had 1 day, 65 (40%) had 2 days and 22 (13%) had 3 days of collection. For patients requiring multiple days of collection, there was no substantial day-by-day decline in apheresis yield. In fact, median yield on days 2 and 3 were 106% and 97% of yield from day 1. There were no severe adverse toxicities from the mobilization regimen. All patients who have undergone transplantation successfully engrafted neutrophils and platelets. Average estimated cost of mobilization drugs with PEG + plerixafor was $14,588, comparable to estimated cost for FIL + plerixafor ($15,399) and TBO + plerixafor ($13,693). Since FIL and TBO are dosed daily and dose is weight-based, the cost comparison with PEG is greatly influenced by patient weight and number of apheresis sessions required (Figure).
Conclusion: PEG plus plerixafor is a convenient, safe, effective and predictable regimen for auto-HPC mobilization. In this setting, PEG cost is comparable to FIL or TBO, being potentially cost-saving in heavier patient.
Saad: Actinium: Consultancy; Spectrum: Honoraria.
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