Outcomes of Matched Sibling and Haploidentical Donors Hematopoietic Stem Cell Transplantation for Pediatric Severe Aplastic Anemia: A Retrospective Multicenter Study.

Background: Acquired aplastic anemia (AA) is a life-threatening hematologic disorder characterized by bone marrow failure. This study evaluates clinical outcomes of matched sibling donor hematopoietic stem cell transplantation (MSD-HSCT) and haploidentical HSCT (haplo-HSCT) in pediatric patients with severe (SAA) and very severe aplastic anemia (VSAA) in Colombia. Methods: A retrospective multicenter study was conducted in four high-complexity centers in Colombia between 2011 and 2021, including 59 pediatric patients with SAA/VSAA who underwent allo-HSCT. Eligible patients were divided into two groups: one group underwent MSD-HSCT and the other haplo-HSCT, either as first-line treatment or after immunosuppressive therapy (IST) failure. Clinical outcomes, graft failure, graft-versus-host disease (GVHD), and overall survival (OS) were analyzed. Results: A total of 59 patients with SAA/VSAA undergoing allo-HSCT were included, 29 undergoing MSD-HSCT and 30 undergoing haplo-HSCT. The 2-year OS for the cohort was 81%, with 85% for MSD-HSCT and 75% for haplo-HSCT. Modified Baltimore-based conditioning regimens in haplo-HSCT showed an OS of 83%. Primary graft failure occurred in two haplo-HSCT patients. Grades III–IV acute GVHD and moderate–severe chronic GVHD were more common in haplo-HSCT. Infection was the leading cause of posttransplant mortality. Conclusion Pediatric SAA patients undergoing MSD-HSCT had better survival outcomes and less incidence of aGVHD compared to haplo-HSCT. Haplo-HSCT with modified Baltimore conditioning offers a viable alternative, particularly when an MSD is unavailable. Prospective studies are needed to confirm these findings.