Impact of stem cell dose on hematopoietic recovery in autologous blood stem cell recipients

Hematopoietic recovery rates following high-dose chemotherapy in autologous blood stem cell recipients have been shown, in part, to be dependent on the source and quantity of hematopoietic stem cells infused. Mobilized blood stem cell quantity (identified by the surface expression of the CD34 antigen) has been demonstrated in multiple studies to be the strongest predictor of days to hematopoietic recovery (ie platelets and neutrophils) in autologous blood stem cell recipients. Additionally, data from four large studies confirm that prompt and sustained hematopoietic recovery will occur in the majority of patients treated with high-dose chemotherapy if a stem cell dose 5 × 10⁶/kg is administered. However, multiple aphereses are needed in the majority of patients to achieve these optimal stem cell doses. Problems associated with multiple aphereses procedures include hypocalcemia, anemia, thrombocytopenia, infection, thrombosis, increased costs, and malignant cell contamination of the apheresis product. Recent data indicate that less differentiated (eg CD33⁻) stem and progenitor cells result in both early and sustained hematopoietic recovery in bone marrow and blood stem cell recipients. Future trials using new growth factors such as stem cell factor (which has been shown to increase CD34⁺/CD33⁻ cell mobilization), as well as improvements in purging strategies are needed to ensure prompt, sustained, and malignant-cell-free engraftment for the majority of autologous blood stem cell recipients.