Utilization of an Algorithm for Chemomobilization Including the Use of Plerixafor in Poor Mobilizers

Background: Chemotherapy plus GCSF has been an effective modality for the mobilization of peripheral blood stem cells. However, the optimal drug, dose, and schedule have not been established. Additionally, the role of plerixafor in chemomobilization protocols has not been clearly described. We developed a chemomobilization algorithm using a 2-day infusion of etoposide at 300 mg/m² followed by GCSF. The algorithm included a predetermined decision point for the addition of plerixafor for poor mobilizers. The purpose of this study is to prospectively evaluate the safety and efficacy of this algorithm in patients undergoing chemomobilization ahead of autologous HSCT.

Methods: Patients underwent chemomobilization using etoposide at a dose of 300 mg/m² daily for 2 days, followed by filgrastim 10 mcg/kg starting on day 3. At day 12, patients began WBC screening, and once the WBC count rose to > 2 x 10^9/L, CD34+ screening began. If the CD34+ count was >20/uL, patients proceeded to collection. If the CD34+ count was <20/uL, plerixafor was added. Patients who required plerixafor to reach a CD34+count >20/uL remained on plerixafor daily until their collection goal was met. The CD34+ stem cell collection goal was 4 x 10⁶ cells/kg, with a minimum requirement of 2 x 10⁶ cells/kg to proceed to HSCT.

Results: To date, 21 patients (14 lymphoma, 5 multiple myeloma, and 2 other) have been treated with our algorithm. Four of the five patients with multiple myeloma had received > 6 cycles of lenalidomide. Of the 21 patients, 18 were successfully mobilized using etoposide plus filgrastim alone. The 3 patients who had inadequate CD34+ mobilization with etoposide plus filgrastim all responded to the addition of plerixafor. To date, 16 of the 21 patients have successfully been transplanted, with the remaining 5 expected to complete SCT within the next month. Patients collected with an average of 1.4 apheresis sessions and collected an average of 6.23 x 10⁶ CD34+ cells/kg. Four patients (19%) were hospitalized due to febrile neutropenia during the course of mobilization.

Conclusion: We demonstrated a successful algorithm-based approach to chemomobilization that included a predetermined strategy to include plerixafor for poor mobilizers.