CD34 + cell dose - Predictors and effect on patient outcome in hematopoietic stem cell transplant

Objectives: In stem cell transplantation, engraftment is the first desired outcome. Although engraftment depends on many factors, stem cell dose is one of the important, modifiable factors. CD34 + cells quantify the dose of hematopoietic stem cell (HSC)for transplant. Material and Methods: A retrospective analysis (2016–2022) was conducted on all hematopoietic stem cell transplant (HSCT) cases. Regression analysis evaluated pre-procedure mononuclear cell count (MNC), total leucocyte counts (TLC), their increments, and pre-CD34 + cell count with CD34 + cell product yield and receiver operating characteristic (ROC) derived minimum threshold of significant predictors for adequate yield. Engraftment, overall survival, relapse, graft vs host disease (GvHD), primary graft failure, and non-relapse related mortality were analyzed across three dose categories: 7X10 6 /kg. Results: Total 78 HSCT procedures (allogenic: autologous=50:28) in 63 patients were analyzed. TLC (r= 0.01, p =0.89) and MNC (r=0.37, p =0.92) weakly correlated with CD34 + cell yield, while TLC increment was moderately correlated, approaching significance (r=0.58, p =0.07). Peripheral blood (PB) CD34 + cells/µL strongly correlated with product CD34 + cells/µL (r=0.71, p =0.006) with 27.25 CD34 + cells/µL (AUC= 85.7%) predicting >4 × 10 6 cells/kg yield (92.9% sensitivity, 75% specificity). Six-year overall survival (OS) was 61.91%. The cumulative incidence of engraftment, relapse (RI), primary graft failure (PGF), non-relapse related mortality (NRM), and GvHD was 85.7%, 22.4%, 16.4%, 9.7%, and 18.6%, respectively. Dose category III (hazard ratio [HR]: 3.82, 95% confidence interval [CI]: 1.0-13.5, p =0.03) had poor OS with no other dose associations with outcomes. Conclusion: A threshold of 27.25 CD34 + cells/to predict >4 × 10 6 cells/kg yield was established. TLC increment correlates with CD34 + yield. For all HSCTs, a higher CD34 + cell dose negatively affected OS; no association was seen in subcategorization into allogenic and autologous transplants. Gender, age, engraftment, and gender heterogeneity affected outcomes.