Total body irradiation versus chemotherapy myeloablative conditioning in B-cell acute lymphoblastic leukaemia patients with first complete remission.

The best conditioning for hematopoietic stem cell transplantation (HSCT) in acute lymphoblastic leukemia is debated. We analyzed 178 adults undergoing HSCT with total body irradiation (TBI) or chemotherapy conditioning regimens for B-cell leukemia in complete remission 1 (CR1). Both TBI and chemotherapy regimens showed comparable overall survival (OS) and leukemia-free survival (LFS). However, TBI had a trend of reduced relapse (HR 0.56, P = 0.064) but higher non-relapse mortality (NRM, HR 3.23, P = 0.072) due to increased grade 3 to 4 graft-versus-host disease (22.8% vs. 8.8%, P = 0.023). The key factor affecting survival was minimal residual disease (MRD) after three chemotherapy cycles (OS P = 0.004, LFS P = 0.006). In MRD-negative patients, both regimens gave similar LFS and cumulative incidence of relapse (CIR) irrespective of whether the transplantation was allogeneic (allo-HSCT) or autologous (auto-HSCT), but the allo-HSCT group had a lower OS due to higher NRM (5.3% vs. 20.6%, P = 0.020). For MRD-positive patients, TBI was superior in LFS (71.9% vs. 43.9%, P = 0.017) and relapse rate (18.5% vs. 48.7%, P = 0.006). Our research indicates the choice between TBI and non-TBI should be based on MRD after three chemotherapy cycles.