Pre-mobilization therapy blood CD34+ cell count predicts the likelihood of successful hematopoietic stem cell mobilization

We examined pre-mobilization blood CD34+ cell count to predict ability to mobilize adequate peripheral blood progenitor cells (PBPC) in 106 cancer patients and 36 allogeneic donors. Mean pre-mobilization therapy blood CD34+ cell count was 3.1 cells × 106/l (s.d.=3.9, r=0.3–37) and mean CD34+ cells collected were 5.3 × 106 cells/kg/leukapheresis procedure (s.d.=7.0, r=0.03–53). Yields correlated with pre-mobilization CD34+ cells × 106/l (r=0.37, P-value<0.0001); correlation was stronger in allogeneic donors (r=0.56, P-value=0.0004) and males (r=0.46, P-value<0.0001). Based on classification and regression tree multivariate analysis, the predictive value of pre-mobilization blood CD34+ cell count was confounded by other variables, including age, gender, mobilization regimen and malignancy type. We generated an algorithm to predict a minimum PBPC yield of 1 × 106 CD34+ cells/kg/leukapheresis procedure after mobilization. A threshold pre-mobilization blood CD34+ cell count of 2.65 cells × 106/l was the most important decision point in predicting successful mobilization. Only 2% of subjects with pre-mobilization blood CD34+ cell counts >2.65 cells × 106/l did not achieve the minimum per apheresis, whereas 24% with pre-mobilization values below threshold had inadequate mobilization. Prospectively identifying individuals at risk for mobilization failure would allow for improved treatment planning, resource utilization and time saving.