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Adult B-cell precursor acute lymphoblastic leukemia (BCP-ALL) with t(4;11)(q21;q23);KMT2A/AFF1is a poor-prognosis entity. This registry-based study was aimed to analyze outcome of patients with t(4;11) BCP-ALL treated with allogeneic hematopoietic stem cell transplantation (alloHSCT) in first complete remission (CR1) between 2000 and 2017, focusing on the impact of measurable residual disease (MRD) at the time of transplant. Among 151 patients (median age, 38) allotransplanted from either HLA-matched siblings or unrelated donors, leukemia-free survival (LFS) and overall survival (OS) at 2 years were 51% and 60%, whereas relapse incidence (RI) and non-relapse mortality (NRM) were 30% and 20%, respectively. These results were comparable to a cohort of contemporary patients with diploid normal karyotype (NK) BCP-ALL with equivalent inclusion criteria (n= 567). Among patients with evaluable MRD pre-alloHSCT, a negative status was the strongest beneficial factor influencing LFS (hazard ratio [HR] = 0.2, p< 0.001), OS (HR = 0.14, p< 0.001), RI (HR = 0.23, p= 0.001), and NRM (HR = 0.16, p= 0.002), with a similar outcome to MRD-negative NK BCP-ALL patients. In contrast, among patients with detectable pretransplant MRD, outcome in t(4;11) BCP-ALL was inferior to NK BCP-ALL (LFS: 27% vs. 50%, p= 0.02). These results support indication of alloHSCT in CR1 for t(4;11) BCP-ALL patients, provided a negative MRD status is achieved. Conversely, pre-alloHSCT additional therapy is warranted in MRD-positive patients.

HLA-matching largely contributes to unrelated donor hematopoietic cell transplantation (UD-HCT) success but, due to the selective deletion of alloreactive T-cells, post-transplantation cyclophosphamide (PTCy) could modulate its negative impact on outcomes. We retrospectively compared acute leukemia patients receiving 10/10 or 9/10 HLA allele-matched UD-HCT with PTCy-GvHD prophylaxis between 2010 and 2017, reported to EBMT registry. The 100-day incidence of grade =2 and grade =3 aGvHD were comparable for 10/10 and 9/10 UD (28% versus 28%, p?=?0.8 and 10% versus 8%, p?=?0.5, respectively). The 2-year cGvHD and extensive cGvHD were similar between 10/10 and 9/10 UD (35% versus 44%, p?=?0.2 and 21% versus 20%, p?=?0.6, respectively). The 2-year nonrelapse mortality was 20% after 10/10 and 16% after 9/10 UD-HCT (p?=?0.1). Relapse incidence at 2-year was 24% for 10/10 and 28% for 9/10 UD-HCT (p?=?0.4). Leukemia-free survival at 2-year was the same for 10/10 and 9/10 UD (56 and 56%, p?=?0.6, respectively), with comparable overall survival (62 and 59%, p?=?0.9, respectively). Multivariate analysis showed no effect of HLA-matching on outcomes. An advanced disease status and patient disability remained the most important factors portending a worse survival. PTCy could alleviate the detrimental effect of HLA-allele mismatching in UD-HCT, potentially expanding the donor pool for acute leukemia patients.