Total marrow irradiation-based conditioning for allogeneic hematopoietic stem cell transplantation in patients with hematologic malignancies: A multicenter real-world study

Currently, there is very limited large-scale real-world data on the use of total marrow irradiation (TMI) as conditioning for allogeneic hematopoietic stem cell transplantation (allo-HSCT). The primary objective of this study was to evaluate the real-world feasibility, efficacy, and safety of TMI-based conditioning in a large multicenter cohort. We retrospectively included consecutive patients undergoing allo-HSCT with TMI-based conditioning across four Chinese centers (2017-2024). The primary endpoint was overall survival (OS); secondary endpoints included disease-free survival (DFS), graft-versus-host disease-free/relapse-free survival (GRFS), nonrelapse mortality (NRM), graft-versus-host disease (GVHD), and safety. Among 205 patients, acute lymphoblastic leukemia (ALL) was the predominant diagnosis (81.5%). With a median follow-up of 19.3 months among survivors, 2-year OS, DFS, and GRFS were 71.7%, 60.0%, and 37.8%, respectively. One-year cumulative incidences of relapse and NRM were 20.2% and 13.8%. Day-100 grade II-IV acute GVHD occurred in 32.9%, and 1-year moderate-to-severe chronic GVHD in 19.1%. In multivariable analyses, acute myeloid leukemia (AML) diagnosis, haploidentical donor, and Eastern Cooperative Oncology Group (ECOG) performance status >1 were associated with inferior outcomes. Exploratory dose-stratified analyses were performed. Severe toxicities within 100 days were infrequent, predominantly infections (21.46%). In this large multicenter cohort, TMI-based conditioning demonstrated real-world feasibility with encouraging survival and manageable safety outcomes.