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Updated: Aug 21, 2026
Busulfan as a Myelosuppressive Agent for Generating Stable High-level Bone Marrow Chimerism in Mice
Published on: April 1, 2015
Feasibility of 8 Gy TBI-Busulfan-Fludarabine Conditioning With Post-Transplant Cyclophosphamide for Pediatric
Jae Won Yoo1, Suejung Jo1, Seongkoo Kim2
1Department of Pediatrics, Division of Pediatric Hematology and Oncology, Catholic Hematology Hospital, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea.
Abstract:
Total body irradiation (TBI)-based myeloablative conditioning is standard for pediatric acute lymphoblastic leukemia (ALL) undergoing allogeneic hematopoietic cell transplantation (HCT), but conventional 12 to 13.2 Gy TBI carries significant long-term toxicities, and pediatric data on reduced-dose TBI combined with post-transplant cyclophosphamide (PTCy) remain limited. To evaluate the feasibility of a reduced-dose 8 Gy TBI-busulfan-fludarabine (TBI-Bu-Flu) regimen with PTCy-based graft-versus-host disease (GVHD) prophylaxis in pediatric high-risk or relapsed ALL undergoing alternative donor HCT. We retrospectively analyzed 37 consecutive pediatric patients (≤18 years at diagnosis) who underwent alternative donor HCT (unrelated, n = 8; haploidentical, n = 29) between 2019 and 2024. All received G-CSF-mobilized peripheral blood stem cell grafts. Pretransplant measurable residual disease (MRD) was negative in 25 of 32 evaluable patients (78.1%). All patients engrafted with complete donor chimerism by day +30. The cumulative incidence of grade II-IV acute GVHD, grade III-IV acute GVHD, and severe chronic GVHD was 51.4%, 10.8%, and 8.8%, respectively. With a median follow-up of 32.7 months, 3-year leukemia-free survival (LFS) and overall survival (OS) were 79.6% and 88.3%, respectively, with a relapse incidence of 20.4% and no observed nonrelapse mortality (NRM). For 26 patients transplanted in CR2, 3-year LFS and OS were 77.7% and 91.3%, respectively. Pretransplant MRD negativity was the only significant prognostic factor for both LFS and OS (P < .001). Eight Gy TBI-Bu-Flu with PTCy is a feasible reduced-radiation conditioning platform, providing reliable engraftment and encouraging leukemia control with no NRM in pediatric high-risk or relapsed ALL. However, the GVHD incidence was higher than anticipated, indicating that the prophylaxis backbone should be optimized in future prospective studies with systematic late-effect monitoring.
