Pegfilgrastim 6 Mg Versus 12 Mg for Autologous Stem Cell Mobilization in Multiple Myeloma Patients: Efficacy, Safety, and Cost Analysis

Background: Autologous hematopoietic cell transplantation (aHCT) is an established treatment for many multiple myeloma (MM) patients. Previous studies have shown pegfilgrastim (PEG) to be a superior hematopoietic cell mobilizing agent in autologous donors in the setting of "just in time" use of plerixafor in patients who don't reach optimal CD34+ in peripheral blood prior to apheresis (PB-CD34+) with filgrastim alone. While most experience is based on PEG 12 mg, we hypothesized that PEG 6mg would lead to similar efficacy and be more cost effective than PEG 12 mg, leading to a practice change in 2014. We have conducted a retrospective analysis comparing the performance of PEG 12 mg (pre change) and PEG 6 mg (post change) for mobilization of hematopoietic progenitor cells in patients with MM at MUSC.

Methods: During the period covered in the analysis (Feb 2013 to June 2015) all MM patients undergoing first mobilization received PEG with initiation of apheresis on the 4^th day if PB-CD34+ ≥ 25/mm³. Otherwise patients received plerixafor 240 µg/kg in the evening of the 4^th day and started collection on the 5^th day. Daily apheresis was continued until a target of 6 x 10⁶ CD34+/Kg was met, limiting toxicities developed, or the patient completed 4 apheresis sessions. In the data analysis, patients were divided based on the dosage of PEG received, 12 mg or 6 mg, and the following information was collected: demographics, date of start of mobilization, number of apheresis days, apheresis yield (CD34+cells/kg), "just in time" use of plerixafor, date of transplantation, time to neutrophil and platelet engraftment, and length of hospital stay,. Mobilization costs included PEG US$ 2290 for a 6-mg vial and plerixafor US$ 5350 for a 24-mg vial (PHS pricing). The daily charges associated with apheresis were based on our program's historical charges of US$ 6922.00 per day of apheresis.

Results: A total of 119 MM patients undergoing upfront mobilization were identified, with 62 patients receiving PEG 6 mg and 57 patients receiving PEG 12 mg. There were no statistical differences in the age, gender, BMI distributions and prior use of lenalidomide between the patients in PEG 6 mg group versus 12 mg group. The proportion of patients in the 6mg group receiving plerixafor (62.9%) was not statistically different from that of patients in the 12mg group (56.1%) (p= 0.5). There was no statistically significant difference in the distribution of CD34+ apheresis yield between the 6mg group (8x10⁶) versus the 12 mg group (7.4x10⁶) (p= 0.2) or in the proportion of patients reaching the CD34+ target in the 6mg (85.4%) compared with 12 mg group (73.7%) (p= 0.1). In addition, no significant difference was detected in the average time to ANC engraftment (15 days for both) or platelet engraftment (21 days for both) between the two groups. Mean duration of hospitalization was 5 days in both arms (p= 0.7), and no major complications or drug toxicities were identified. No statistical difference was noted in the number of apheresis days (6 mg: 1.8 vs 12 mg: 1.7) between both groups (p= 0.3). The median total cost of collection per patient was lower in the PEG 6 mg group at US$ 16134 versus US$ 18424 in PEG 12 mg group. Interestingly, the mean age of patients who required plerixafor (64 years) was significantly higher than that of patients who did not require plerixafor (57 years) (p-value=0.00).

Conclusion: The use of PEG 6mg for autologous hematopoietic cell mobilization in MM patients is more cost-effective and yields similar results when compared with the use of PEG 12 mg. There is no significant correlation between the use of plerixafor and the dosage of PEG used. Plerixafor tends to be more utilized by older patients in both groups. Overall, this single institution study provides rationale for the use of PEG 6 mg instead of PEG 12 mg for CD34+ mobilization in MM patients.