Similar dynamics of intraapheresis autologous CD34+ recruitment and collection efficiency in patients undergoing mobilization with or without plerixafor

Background Compared with growth factor (G) alone, the combination of G with plerixafor (G + P) increases peripheral blood CD34+ count (PB-CD34+) and improves CD34+ collection yield (yCD34+) in multiple myeloma and lymphoma patients undergoing autologous hematopoietic progenitor cell (AHPC) mobilization. It is unknown whether the improved yCD34+ with G + P results entirely from expansion of PB-CD34+ or also from increased intraapheresis CD34+ recruitment and collection efficiency. Study Design and Methods We retrospectively studied 192 patients who underwent AHPC mobilization and collection with G (n = 73) or G + P (n = 119) to compare the adjusted relative efficiency (aRE), the proportion of the circulating CD34+ pool that is captured for each blood volume processed. Additionally, in a prospective cohort of nine patients mobilizing with G and 11 with G + P, PB-CD34+ after leukapheresis allowed calculation of the recruitment coefficient (RC), proportion of the initial CD34+ pool recruited from the marrow into peripheral blood for each blood volume processed. Results There was no difference in aRE between G and G + P (0.50 vs. 0.46; p = 0.37) and no substantial decline in aRE with higher blood volumes processed in either group. RC was also not different between G and G + P (median, 0.39 and 0.38, respectively; p = 0.7). Prediction of yCD34+ was determined essentially by PB-CD34+ and not affected independently by plerixafor. Conclusion Kinetics of intraapheresis CD34+ recruitment and collection is proportional to PB-CD34+ but not influenced further by plerixafor.