TBI, etoposide, and cyclophosphamide conditioning for intermediate-risk relapsed childhood acute lymphoblastic leukemia.

BACKGROUND: In children with intermediate-risk relapsed acute lymphoblastic leukemia (ALL), allogeneic hematopoietic stem cell transplantation (allo-HSCT) has markedly improved the outcome of patients with an unsatisfactory minimal residual disease (MRD) response. Total body irradiation (TBI), etoposide (ETP), and cyclophosphamide (CY) have been shown to be equivalent to or better than TBI + ETP for conditioning, so we hypothesized that even greater survival could be achieved due to recent advances in HSCT and supportive care.

PROCEDURE: We prospectively analyzed the efficacy and safety of allo-HSCT with a unified conditioning regimen of TBI + ETP + CY in children with intermediate-risk relapsed ALL, based on MRD in the bone marrow after induction, from the Japanese Pediatric Leukemia/Lymphoma Study Group (JPLSG) ALL-R08-II nationwide cohort (UMIN000002025).

RESULTS: Twenty patients with post-induction MRD ≥ 10-3 and two not evaluated for MRD underwent allo-HSCT. Engraftment was confirmed in all patients, and no transplantation-related mortality was observed. The 3-year event-free survival and overall survival rates after transplantation were 86.4% ± 7.3% and 95.5% ± 4.4%, respectively.

CONCLUSION: Allo-HSCT based on post-induction MRD with TBI + ETP + CY conditioning was feasible in Japanese children with intermediate-risk relapsed ALL.