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 cel l transplantation (PBSCT) over bone marrow transplantation (BMT), if any, h ave not been seriously evaluated in a pediatric population. We report here our experience with this procedure and demonstrate rapid engraftment to red uce procedure-related complications and enhanced allogeneic immune reaction to reduce leukemic relapse. Methods: The feasibility of PBSCT was reviewed retrospectively. Four patien ts (2 AML and 2 ALL, aged 8-18 years) underwent allogeneic PBSCT for relaps ed leukemia after primary allogeneic BMT (n = 2), for active hepatosplenic fungal abscess (n = 1) or for refractory relapse with conventional chemothe rapy (n = 1). Four healthy donors (aged 10-49 years) received granulocyte c olony-stimulating factor (G-CSF) 10 mug/kg/day by subcutaneous injection fo r 5 days. An individualized cytoreductive regimen was used before transplan tation. Results: No significant toxicities were observed in normal donors on G-CSF treatment or at collection of PBSC. After PBSCT, no significant acute toxic ities were observed and the median duration to an absolute granulocyte coun t of 0.5 x 10(9)/l and a platelet count of 20 x 10(9)/l was 16 and 21 days, respectively. Although none of our patients developed acute graft-versus-h ost 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 popula tion with fewer acute complications, although the potential risk of G-CSF t reatment in normal donors should be seriously weighed against the existing risks of marrow aspiration under general anesthesia. The risk of chronic GV HD may need to be balanced against a possible graft-versus-leukemia benefit in patients at higher risk of leukemic relapse.