High Failure-Free Survival after Unrelated Donor Peripheral Blood Stem Cell Transplantation in Pediatric Severe Aplastic Anemia

The use of alternative donor peripheral blood stem cell transplantation (PBSCT) has increased in recent years. In this study, we analyzed the effect of stem cell source and HLA disparity on outcomes in pediatric patients with severe aplastic anemia (SAA). A total of 134 patients who underwent HSCT with nonmyeloablative conditioning between 2006 and 2020 were enrolled and classified into 3 groups: HLA-matched bone marrow transplantation (M-BMT; n = 24), HLA-matched PBSCT (M-PBSCT; n = 66), and HLA-mismatched PBSCT (MM-PBSCT; n = 44). Significantly higher stem cell doses were obtained for PBSCT than for BMT. A total of 13 patients experienced secondary graft failure (GF), with a cumulative incidence (CI) of 10.0%. HLA-mismatched PBSCT and a very severe degree of disease significantly decreased the incidence of secondary GF. The CI of grade II-IV acute graft-versus-host disease (GVHD) was significantly higher in PBSCT than in BMT, but the CI of grade III-IV acute GVHD and CI of chronic GVHD requiring systemic treatment did not increase in PBSCT. The estimated 5-year overall survival (OS), failure-free survival (FFS), and GVHD-free failure-free survival (GFFS) of the total cohort were 93.0%, 89.5%, and 77.5%, respectively. The most favorable FFS was observed in the MM-PBSCT group (97.6%; P = .03), whereas OS and GFFS were similar across the 3 groups. In multivariate analysis, HLA mismatch and short time from diagnosis to transplantation were associated with superior FFS. Unrelated donor PBSCT with low-intensity SAA conditioning showed favorable outcomes in terms of low rate of secondary GF, higher FFS, and manageable GVHD regardless of HLA compatibility. Our findings suggest the feasibility of PBSCT from unrelated donors, resulting in the possible expansion of the donor pool in transplantation for pediatric SAA.