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.

Prediction of poor mobilization of autologous CD34+ cells with growth factor in multiple myeloma patients: implications for risk-stratification.

It is unknown whether clinical characteristics can successfully predict which multiple myeloma (MM) patients would be poor mobilizers with growth factor (GF) alone so they can be assigned to mobilization with chemotherapy + GF or GF + plerixafor. MM patients (N = 477) who underwent autologous mobilization with GF were retrospectively reviewed and assigned into training and validation cohorts. In multiple regression analysis, age, platelet count at time of mobilization, type of GF utilized, and extent of exposure to lenalidomide independently correlated with peripheral blood (PB)-CD34+ and were integrated in a predicting score (PS) for poor mobilizers, defined as PB-CD34+ < 20/mm(3) 4 days after initiation of GF. There was no correlation between institution, gender, time between diagnosis, and mobilization or plasma cells in the bone marrow at time of mobilization and PBCD34+. The PS cut-off found in the training cohort to have 90% sensitivity for prediction of poor mobilizers performed with 89.7% sensitivity but only 34.8% specificity in the validation cohort. Conversely, the PS cut-off developed to have 90% specificity performed with 86.9% specificity but only 37% sensitivity. We conclude that clinical characteristics identifiable before initiation of mobilization should not be used to stratify MM patients for different mobilization strategies.