Evaluation of a Risk-Based Algorithm for the Utilization of Plerixafor As Primary Mobilization of CD34+ Cells in Autologous Hematopoietic Cell Transplant Candidates,
Authors: Shapiro Jamie , Perkins Janelle , Bookout Ryan , Tombleson Rebecca , Ayala Ernesto , Janssen William E. , Anasetti Claudio , Fernandez Hugo F. 
Published: October 2019

Abstract
Abstract 4060
Study Purpose and Methods: Following FDA approval of plerixafor, our institution developed practice guidelines using a risk-based algorithm to optimize the use of plerixafor for CD34 cell mobilization in autologous hematopoietic cell transplant (HCT) candidates. We defined patients (pts) at high risk for mobilization failure and eligible to receive G-CSF 10 mcg/kg/day for 4 days with plerixafor 0.24 mg/kg added on day 4 if they met any of the following criteria: 1) 3 or more lines of prior chemotherapy; 2) 2 or more lines of prior chemotherapy plus a radioimmunoconjugate or extensive field radiation therapy (XRT); 3) 4 or more cycles of hyper-CVAD, 4) 4 or more cycles of lenalidomide; or 5) hypocellular bone marrow (<25% cellularity) prior to mobilization. Apheresis began on day 5 of mobilization for all pts. Pts not meeting this criteria received G-CSF alone unless the first day apheresis yield was less than 0.5 million CD34 cells/kg or peripheral CD34 count was <10/μmL in which case plerixafor was added. In order to evaluate the efficacy of plerixafor in these high risk patients and validate the risk categories, we conducted a retrospective review of consecutive pts mobilized before and after guideline institution. The primary endpoint was the proportion of pts collecting 2 million CD34 cells/kg in one apheresis.

Results:
415 pts were mobilized between 1/1/2008–8/31/10, 334 received G-CSF and 81 received G-CSF and plerixafor. G-CSF pts received 10 or 20 mcg/kg/day for 4 days, depending on institutional practice. This analysis includes those determined to be high risk by the above listed categories: 124 G-CSF pts and 72 plerixafor pts. The most common high risk categories represented were 3 or more lines of prior chemotherapy (group 1): 61 G-CSF pts and 27 plerixafor pts; 4 or more cycles of hyperCVAD (group 2): 14 G-CSF pts and 15 plerixafor pts; and 4 or more cycles of lenalidomide (group 3): 31 G-CSF pts and 27 plerixafor pts. For group 1 patients 38% of G-CSF pts collected >2 million in one apheresis compared to 67% of plerixafor pts (p=0.014). For group 2 pts, the respective proportions were 21% vs 47% (p=0.153) and for group 3 pts, the respective proportions were 39% vs 100% (p<0.001).

Conclusions:
Our results validate the risk categories used in our guidelines since less than 50% of high risk G-CSF patients analyzed were able to mobilize a sufficient number of CD34 cells with one apheresis. In addition, plerixafor was associated with a larger proportion of pts who collected 2 million CD34 cells/kg in one apheresis, suggesting superior efficacy in these high risk patients. We conclude that there are specific pts that should receive plerixafor in order to reduce the number of aphereses necessary to proceed to HCT. This may be a more reliable and efficient practice than assessing peripheral CD34 counts prior to apheresis as these counts may not always accurately predict CD34 yield or be available in a timely manner.

Disclosures:
Shapiro: Genzyme: Research Funding, Speakers Bureau. Perkins:Genzyme: Research Funding. Bookout:Genzyme: Research Funding. Fernandez:Genzyme: Membership on an entity's Board of Directors or advisory committees, Research Funding.