Mobilization and transplantation of peripheral blood stem cells

Two hundred nineteen patients underwent peripheral blood stem cell (PBSC) transplantation from 1990 to 1997. Stem cells were mobilized with cyclophosphamide (CY), or with CY plus Taxol or etoposide, followed by cytokines, and collected when leukocyte counts > or = 1,000/microl, or when CD34+ counts > or = 20/microl. On average, four to five collections were needed to obtain sufficient PBSC for engraftment. When CD34+ counts were used, the average number of collections decreased from 5.4 to 4.2. A discrepancy was noted in the extraction ratios and number of collections that depended on the optical density (I/O) setting of the leukapheresis machine. Patients collected at a setting of 100 had higher extraction ratios and required fewer collections (mean = 2.7) than those collected at 150 (mean = 4.4). This result was unexpected, because the entire mononuclear cell layer is collected at the higher I/O setting. Further analysis revealed that a larger volume of red cells was collected at 150 than at 100. These procedures used a small-volume collection chamber, so the chamber was apparently overloaded by RBC at the higher setting. More rapid recovery of neutrophil counts and platelet counts was seen in PBSC transplants than in autologous marrow transplants; moreover, PBSC transplant patients required fewer RBC and platelet transfusions. Sixteen out of 21 normal donors for allogeneic PBSC transplants gave adequate collections (> 2.5 x 10(6) CD34+ cells/kg), but three donors failed to yield > or = 1.5 x 10(6) CD34 cells/kg. This suggests an inherent difference among certain normal donors that may make PBSC mobilization difficult.