Plerixafor Mobilization in MM Patients and Impact on CD34 Cell Collection and Transplant Outcomes

Background: Plerixafor (Mozobil) has been approved for use in multiple myeloma (MM) and non-Hodgkin lymphoma (NHL) patients (pts) in combination with G-CSF to mobilize hematopoetic stem cells (CD34) in collection for autologous transplant (tx). Many different mobilization approaches exist in this field, and we evaluate the role of Plerixafor in MM and amyloidosis (AL) pts.

Methods: To evaluate plerixafor mobilization in the transplant setting, all MM and AL patients who were mobilized for autologous stem cell transplant (autoSCT) between 2010 and 2012 were included. Sufficient CD34+ cell collection was defined both using a minimal cutpoint of 2x10⁶ as well as an optimal goal of 5x10⁶ CD34 cells. Significant influences on the ability to achieve these collection goals on day 1 and across all collections were evaluated using univariate logistic regression models in addition to graphical analyses and two sample tests. In addition to clinical characteristics, we assessed the impact of plerixafor mobilization use and also lenalidomide and thalidomide use on these outcomes.

Results: Overall, 196 pts (10 AL, 182 MM, 4 MM/AL) were mobilized for autoSCTs from 2010-2012. Most pts were male (60%), most were Caucasian (88%), and the median age at transplant was 59 years (range: 18 to 73). About half of pts (52%) received lenalidomide (lena), and only 5% received thalidomide prior to mobilization; the median number of lena cycles was 4 (range: 1 to 11). Comorbidity indices were similar to those who did vs. did not receive plerixafor (p=0.8). On day 1 collections, 154 pts achieved a yield of >2x10⁶ and 87 pts >5x10⁶ CD34+ cells. Across all collections, all but 2 pts had a total yield of at least 2 million CD34 cells, and 152 had at least 5x10⁶ CD34 cells. Several factors appeared to influence a pts ability to achieve a yield of >5x10⁶ CD34+ cells: age (OR=0.94, p=0.014), day 1 yield of >2x10⁶ CD34+ cells (OR=14.5, p<0.0001), and the total number of collections (OR=0.32, p<0.0001). Days to ANC recovery after transplant was also borderline associated with a total yield of at least 5x10⁶ CD34+ cells (OR=0.82, p=0.075). While lena use was not significantly associated with total yield of 5 million CD34+ cells, pts who had prior lena were less likely to achieve a yield of at least 2x10⁶ CD34+ cells on day 1 collection vs. those who did not (OR=0.48, p=0.045). Prior radiation therapy was not significantly associated with any of the collection goal metrics. Plerixafor use was not significantly associated with the ability to achieve a yield of 5x106 CD34+ cells on day 1 or in total; however, plerixafor use was significantly associated with not achieving a day 1 collection of at least 2x10⁶ CD34+ cells (OR=0.24, p=0.0007); however, this is likely due more to the decision algorithms used to determine administration of plerixafor for mobilization prior to autoSCT than a statement on the effectiveness of plerixafor as a mobilizing agent.