Use of Allogeneic Hematopoietic Stem-Cell Transplantation Based on Minimal Residual Disease Response Improves Outcomes for Children With Relapsed Acute Lymphoblastic Leukemia in the Intermediate-Risk Group

Purpose In children with intermediate risk of relapse of acute lymphoblastic leukemia (ALL), it is essential to identify patients in need of treatment intensification. We hypothesized that the prognosis of patients with unsatisfactory reduction of minimal residual disease (MRD) can be improved by allogeneic hematopoietic stem-cell transplantation (HSCT). Patients and Methods In the Acute Lymphoblastic Leukemia–Relapse Study of the Berlin-Frankfurt-Munster Group (ALL-REZ BFM) 2002, patients with an MRD level of ≥ 10−3 (n = 99) at the end of induction therapy were allocated to HSCT, whereas those with an MRD level less than 10−3 (n = 109) continued to receive chemotherapy. MRD was quantified by real-time polymerase chain reaction for clone-specific T-cell receptor/immunoglobulin gene rearrangements. Results The probability of event-free survival for patients with MRD ≥ 10−3 was 64% ± 5% in ALL-REZ BFM 2002 compared with 18% ± 7% in the predecessor study ALL-REZ BFM P95/96 (P < .001). This was mainly achieve...