CD34+ cell dose and hematologic recovery in allogeneic peripheral blood stem cell transplantation

Allogeneic peripheral blood stem cell transplantation (Allo-PBSCT) has been performed as an alternative to bone marrow transplantation (BMT). Here we report poor mobilization with granulocyte-colony stimulating factor (G-CSF) and engraftment kinetics in Allo-PBSCT. Sixteen patients (aged 6-61 yr, median 34 yr) received allogeneic peripheral blood stem cells from related donors (aged 15-68 yr, median 37 yr) after myeloablative therapy. Nine of the patients had standard-risk disease and 7 had high-risk disease. The donors received G-CSF at a dose of 10 micrograms/kg/day by subcutaneous injection for 4 to 6 days. Peripheral blood stem cells were subsequently collected in 1 to 3 aphereses and infused immediately. All patients received G-CSF after transplantation. Fifteen patients underwent Allo-PBSCT and one underwent Allo-PBSCT plus BMT. The mean number of CD34+ cells infused in the 15 Allo-PBSCT patients was 6.32 x 10(6)/kg (range 1.28-14.20). The outcomes were compared with 9 identically treated patients who underwent Allo-BMT. The median times until engraftment for neutrophils > 500/microliter and platelets > 20,000/microliter were 14 (range 10-17) and 15 (range 11-50) days in the Allo-PBSCT group and 17 (range 13-29) and 20 (range 16-160) days in the Allo-BMT group, respectively (p = 0.0177 and p = 0.003). Three donors were considered to have poor mobilization (< 2 x 10(6) CD34+ cells/kg of the recipient); two of them yielded 1.28 and 1.78 x 10(6) CD34+ cells/kg in 3 apheresis procedures. The patients who received cells from these donors showed prompt neutrophil engraftment, but one showed delayed platelet engraftment and another died of grade IV acute GVHD before reaching 20,000 platelets/microliter. An additional bone marrow harvest was necessary from one donor because of poor mobilization(0.17 x 10(6) CD34+ cells/kg). Thus, Allo-PBSCT results in more rapid engraftment. It will be necessary to clarify the minimum CD34+ cell dose for complete engraftment in a larger series of trials.