Possible clinical benefits of the use of peripheral blood stem cells over bone marrow in the allogeneic transplantation setting for the treatment of childhood leukemia

Background: The benefits of allogeneic peripheral blood stem/progenitor cell transplantation (PBSCT) over bone marrow transplantation (BMT), if any, have not been seriously evaluated in a pediatric population. We report here our experience with this procedure and demonstrate rapid engraftment to reduce procedure-related complications and enhanced allogeneic immune reaction to reduce leukemic relapse. Methods: The feasibility of PBSCT was reviewed retrospectively. Four patients (2 AML and 2 ALL, aged 8-18 years) underwent allogeneic PBSCT for relapsed leukemia after primary allogeneic BMT (n = 2), for active hepatosplenic fungal abscess (n = 1) or for refractory relapse with conventional chemotherapy (n = 1). Four healthy donors (aged 10-49 years) received granulocyte colony-stimulating factor (G-CSF) 10 μg/kg/day by subcutaneous injection for 5 days. An individualized cytoreductive regimen was used before transplantation. Results: No significant toxicities were observed in normal donors on G-CSF treatment or rat collection of PBSC. After PBSCT, no significant acute toxicities were observed and the median duration to an absolute granulocyte count of 0.5 × 10⁹/l and a platelet count of 20 × 10⁹/l was 16 and 21 days, respectively. Although none of our patients developed acute graft-versus-host disease (GVHD), two developed chronic GVHD involving the liver and skin. Among those who developed chronic GVHD, one died of recurrent disease and another died of pneumonia 235 days after PBSCT. The two remaining patients have been alive without evidence of disease with follow-ups of 193 and 123 days, respectively. Conclusions: Allogeneic PBSCT can be a safe procedure in a pediatric population with fewer acute complications, although the potential risk of G-CSF treatment in normal donors should be seriously weighed against the existing risks of marrow aspiration under general anesthesia. The risk of chronic GVHD may need to be balanced against a possible graft-versus-leukemia benefit in patients at higher risk of leukemic relapse.