Clinical Outcomes of B Cell Acute Lymphoblastic Leukemia Patients Treated with Haploidentical Stem Cells Combined with Umbilical Cord Blood Transplantation

Clinical outcomes of hematopoietic stem cell transplantation (HSCT) using a haploidentical stem cell graft and an unrelated umbilical cord blood unit (haplo-cord HSCT) for the treatment of B cell acute lymphoblastic leukemia (B-ALL) remain unclear. This study was conducted to explore the clinical outcomes of haplo-cord HSCT in patients with B-ALL. A total of 112 B-ALL patients who underwent haplo-cord HSCT and 64 B-ALL patients who underwent haploidentical HSCT (haplo-HSCT) at our center between 2010 and 2020 were retrospectively included in this study, and clinical outcomes and prognostic factors were further analyzed. Of the 112 haplo-cord HSCT recipients, 106 (94.6%) achieved complete haploidentical chimerism and 6 (5.4%) had mixed cord blood chimerism. No differences in neutrophil and platelet recovery or in the incidences of graft-versus-host disease, cytomegalovirus/Epstein-Barr virus viremia, bloodstream infection, or hemorrhagic cystitis were observed between the haplo-cord HSCT and haplo-HSCT groups. Compared with the haplo-HSCT group, the haplo-cord HSCT group had a higher absolute number of CD3+ cells (P = .029) and a lower ratio of CD3+CD4+ /CD3+CD8+ cells (P = .049) at 1 month post-transplantation. Moreover, the haplo-cord HSCT group had lower minimal residual disease (MRD) levels at 1 month (P = .020) and 100 days (P = .038) post-transplantation and a better 3-year prognosis (overall survival, P = .016; disease-free survival, P = .041; cumulative incidence of relapse [CIR], P = .016). The CIRs in patients with adverse genomic features (P = .040) or flow cytometry-based MRD (FCM-MRD) ≥1 × 10-4 (P = .033) were improved by haplo-cord HSCT. Multivariate analysis revealed that haplo-cord HSCT could independently improve the 3-year OS, DFS, and CIR of B-ALL patients (OS, P = .029; DFS, P = .024; CIR, P = .024). In addition, allo-HSCT at first complete remission was an independent parameter associated with 3-year OS for B-ALL patients (P = .014). An FCM-MRD ≥1 × 10-4 pre-HSCT could independently predict unfavorable 3-year DFS and CIR (DFS, P = .020; CIR, P = .036) in B-ALL patients. Our data suggest that the use of haplo-cord HSCT can independently improve survival in patients with B-ALL.