Total Body Irradiation Versus Chemotherapy Conditioning in Pediatric Acute Lymphoblastic Leukemia Patients Undergoing Hematopoietic Stem Cell Transplant: A Systematic Review and Meta-Analysis.

Allogeneic hematopoietic stem cell transplant (HSCT) is indicated in pediatric patients with acute lymphoblastic leukemia (ALL) who have relapsed or are at a very high risk of relapse during first complete remission. Two types of myeloablative conditioning are employed before allogeneic HSCT: total body irradiation (TBI)-based regimens and chemotherapy (CHT) alone. This study compares the efficacy and safety of TBI-based regimens and CHT-based conditioning in pediatric, adolescent, and young adult patients with ALL (0-24 years old). TBI-based and CHT-conditioning regimens were evaluated in 4262 and 1367 patients, respectively, from 15 studies. Compared to CHT alone, TBI-based regimens were associated with better overall survival (OS), relative risk (RR) 1.21, better event-free survival (RR 1.34), and a reduced risk of relapse (RR 0.69). Both approaches had comparable risk of acute graft-versus-host disease (GVHD), grades 3 to 4 acute GVHD, chronic GVHD, and nonrelapse mortality (NRM). In the subgroup analysis for patients in first complete remission, TBI-based regimens and CHT alone had comparable OS and NRM. Our results demonstrate the superiority of TBI-based regimens compared to CHT alone in pediatric patients with ALL.