Cord Haploidentical Non-In Vitro T Cell Depletion Allogeneic Hematopoietic Stem Cell Transplantation Reduces Relapse of Refractory Acute Leukemia

Whether a graft-versus-graft (GVG) response in patients undergoing allogeneic hematopoietic stem cell transplantation (HSCT) is associated with an enhanced graft-versus-leukemia (GVL) effect remains highly controversial. Furthermore, it is unknown if the GVG response overwhelms the impact of refractory acute leukemia. We aimed to compare the characteristics and therapeutic outcomes between patients undergoing a modified haploidentical cord blood (cord-haplo) HSCT protocol (n = 97) and those undergoing haploidentical HSCT (n = 42) for refractory acute leukemia. A reliable and stable predominant haploidentical donor chimerism was established. The 2-year relapse rate was more favorable in patients undergoing cord-haplo HSCT than in those undergoing haploidentical HSCT (25.9% versus 53.2%; P = .007), as was progression-free survival (PFS; 35.5% versus 17.9%; P = .049). Meanwhile, nonrelapse mortality at 2 years was not significantly different (38.0% versus 24.6%; P= .367). We also found that a higher number of mutual haploidentical donor-mismatched antigens, a concept similar to HLA mismatching, was associated with better disease control. Multivariate analysis identified cord-haplo HSCT as an independent significant predictor of reduced relapse (hazard ratio [HR], .44; P = .028) and improved PFS (HR, .58; P = .033), as was chronic graft-versus-host disease (GVHD) (relapse: HR, .42; P = .013; PFS: HR, .63: P = .052). However, the incidences of neutrophil and platelet engraftment, GVHD, and virus reactivation were comparable in the 2 groups. This study demonstrates that cord-haplo HSCT significantly enhances the GVL effect and improves PFS, providing a reliable and efficient therapeutic platform for patients with refractory acute leukemia. (C) 2018 American Society for Blood and Marrow Transplantation.