Hematopoietic Progenitor Cell Counts Is a Useful Indicator To Determine Appropriate Time For Peripheral Blood Stem Cell Collection

The optimal peripheral blood stem cell (PBSC) collection is a key step for successful outcome in hematopoietic stem cell transplantation (HSCT). Many indicators including preharvest white blood cell (WBC), mononuclear cell (MNC), and CD34 positive cell counts have been used for deciding the adequate time for collection of PBSCs, but each indicator has limitations. Here we investigated hematopoietic progenitor cell (HPC) count as an indicator for PBSC collection. Methods: Data from 851 autologous PBSC collections from 233 patients at the National Cancer Center, Korea, were analyzed. The correlations between harvested CD34 cell counts with preharvest WBC, MNC, CD34 cell counts, and HPC were analyzed, as were correlations by disease and mobilizing agent. Also how the outcome for engraftment can be predicted based on HPC count was studied. Results: The median age of patients was 41 years (range 0.1-72 years). The most frequent diseases were multiple myeloma (n=64) and non-Hodgkin lymphoma (n=56). The correlation coefficient between collected CD34 cells and preharvest CD34 count was (r=0.669, p<0.001), followed by preharvest HPC count (r=0.419, p<0.001), preharvest MNC (r=0.190, p<0.001) and preharvest WBC (r=0.014, p=0.679). The most adequate cut-off value for obtaining >1x10⁶ CD34+ cells/kg at first time of PBSC was 24.0 HPCs/μL with sensitivity and specificity of 67.7% and 74.3% respectively. The cutoff as 28.0 HPCs/μL was adequate for obtaining 2.0 x10⁶ CD34+ cells/kg with sensitivity and specificity of 73.7% and 72.2% respectively. HPC was well correlated with CD34 in PBSC of patients with multiple myeloma (r=0.326, p=0.009), non-Hodgkin lymphoma (r=0.353, p=0.008), especially diffuse large B-cell lymphoma (r=0.810, p<0.001) and acute leukemia (r=0.998, p<0.001). HPC was a better indicator for non-cyclophosphamide (r=0.337, p<0.001) than cyclophosphamide-based chemomobilization (r=0.572, p=0.052). Infused number of HPCs did not affect the times to engraftment of platelets (p=0.896) and neutrophils (p=0.953), though CD34 count of infusion had positive effect on platelet engraftment (p=0.017). Conclusion: HPC count represented good correlation with CD34+ and high area under the curve. Considering advantages of ease for use and cost-effectiveness than those of CD34 count, HPC is a good surrogate marker to determine appropriate timing for PBSC.

No relevant conflicts of interest to declare.