Effectiveness of an Algorithm-Based Approach to Filgrastim-Based Mobilization Using Predetermined Decision Points for the Inclusion of Plerixafor

Background: The use of filgrastim with or without plerixafor has been shown to be an effective modality for the mobilization of peripheral blood stem cells. However, questions remain as to the CD34+ count that would best predict for efficient collection. We developed a filgrastim-based mobilization algorithm with a predetermined decision point for the inclusion of plerixafor and a CD34+ count of 20 cells/uL as the trigger for collection. The purpose of our evaluation was to determine the efficacy of this algorithm, as well as the impact on plerixafor use, in patients undergoing mobilization with filgrastim prior to autologous hematopoietic stem cell transplant (HSCT).

Methods: Patients received filgrastim 10 mcg/kg SC once daily for 4 days. If the day 5 CD34+ count was > 20/ul, apheresis was started and filgrastim was continued until the collection goal was met. If the day 5 CD34+ count was <10, plerixafor was started, and if the day 5 CD34+ count was 10-20, filgrastim was continued for 1 day with plerixafor added if the day 6 CD34+ count remained <20/uL. Mobilization efforts were stopped if the blood CD34+ count remained < 10. The CD34+ cell collection goal was 4 x 10⁶ cells/kg, with a minimum requirement of 2 x 10⁶ to proceed to HSCT.

Results: To date, 21 patients (18 multiple myeloma and 3 other) have been treated. Fifteen of 18 myeloma patients received prior lenalidomide therapy. Eleven of the 21 patients were successfully mobilized using filgrastim alone. Nine patients who had inadequate CD34+ mobilization with filgrastim alone responded to the addition of plerixafor. Patients requiring plerixafor received an average of 1.56 doses. One patient with non-Hodgkin’s lymphoma had no response to filgrastim and therefore mobilization attempts were halted. Seventeen of the 21 patients have successfully proceeded to transplant, with 3 of the remaining 4 expected to be admitted for HSCT within the next month. Patients collected in an average of 1.7 apheresis sessions and collected an average of 5.15 x 10⁶ CD34+ cells/kg.

Conclusion: We demonstrate here a successful and cost-effective algorithm-based approach to mobilization, including a predetermined strategy to include plerixafor for poor mobilizers. By using a decision point for the inclusion or exclusion of plerixafor, we avoided use of the agent in patients unlikely to need it for successful collection.