Efficacy of Plerixafor with Same Day Administration and Mobilization: A Retrospective Chart Review of Patients with Multiple Myeloma and Lymphoma Undergoing Autologous Stem Cell Transplant

Plerixafor allows for rapid mobilization of hematopoietic stem cells (HSCs) by disrupting the interaction of HSC receptor CXCR4 and bone marrow stromal cytokine SDF-1 alpha. When combined with granulocyte colony stimulating factor (G-CSF) with or without chemotherapy, rates of successful mobilization are increased in patients who have previously failed to mobilize or have traits predictive of failure. Current package labeling for plerixafor states that leukapharesis (LP) should begin 10-11 hours post administration, the time at which peak peripheral blood (PB) CD34+ cell counts have been observed. Phase I data in healthy volunteers shows that peak PB CD34+ cell count is dose dependent and that counts increase in a linear fashion between hours 1,3,6 and 9. Studies in HLA-matched sibling donors have shown that minimum required yield for transplant can be reached when LP begins 4 hours after plerixafor injection. In our institution, due to time constraints, we follow a model consistent with these previous studies and begin LP 4-6 hours after plerixafor injection. In order to assess efficacy of this timing in patients undergoing autologous stem cell transplant (autoSCT), we completed a retrospective chart review of 43 patients; 25 with lymphoma and 18 with multiple myeloma (MM). The median percent change in PB CD34+ cell count, prior to 1^stLP, was 19.9% in lymphoma and 13.45% in MM. 95% of patients reached the minimum yield required for autoSCT in ≤ 4 days. One patient with MM and one patient with lymphoma failed to collect adequate levels of HSCs. The median total CD34+ yield was 4.33x10⁶ and 6.73x10⁶ in the lymphoma and MM groups respectively. All but five patients proceeded to autoSCT. Among the 38 patients that remained eligible for autoSCT, the median number of days for ANC and platelet engraftment was 11 and 22 respectively. These results are comparable to historical data, thus showing that high risk patients can collect an adequate number of stem cells, in an expected period of time, with good engraftment results using an alternative plerixafor mobilization schedule.