Haploidentical transplantation versus umbilical cord blood transplantation in acute myeloid leukemia with measurable residual disease.

Post-transplant cyclophosphamide-based haploidentical transplantation (PTCy-haplo) and umbilical cord blood transplantation (uCBT) have the potential to mitigate the adverse impact of pretransplant measurable residual disease (MRD) on post-transplant survival of patients with acute myeloid leukemia (AML). To compare outcomes between PTCy-haplo and uCBT in patients with MRD-positive AML, we retrospectively analyzed MRD-positive AML patients aged ≥16 years enrolled in the Japanese nationwide registry from 2015 to 2023 who underwent PTCy-haplo (n = 94) or single uCBT (n = 275) as first transplantation. MRD was evaluated by polymerase chain reaction for chimeric genes (n = 139) or Wilms' tumor 1 expression (n = 230). In multivariable analyses, the PTCy-haplo and uCBT groups showed comparable relapse-free survival (RFS) (hazard ratio [HR], 1.06; 95% confidence interval [CI], 0.67‒1.67; P = 0.809), overall survival (HR, 0.92; 95% CI, 0.57‒1.49; P = 0.735), graft-versus-host disease (GVHD)-free RFS (HR, 0.89; 95% CI, 0.61‒1.31; P = 0.560), chronic GVHD (cGVHD)-free RFS (HR, 1.20; 95% CI, 0.81‒1.78; P = 0.368), relapse (HR, 0.78; 95% CI, 0.39-1.57; P = 0.490) and nonrelapse mortality (HR, 1.48; 95% CI, 0.79-2.79; P = 0.230). Compared to the uCBT group, the PTCy-haplo group showed lower incidences of grade II‒IV (HR, 0.60; 95% CI, 0.39-0.92; P = 0.020) and III‒IV acute GVHD (aGVHD) (HR, 0.28; 95% CI, 0.10-0.79; P = 0.016), but a higher incidence of extensive cGVHD (HR, 2.23; 95% CI, 1.16-4.29; P = 0.017). Furthermore, higher likelihoods of neutrophil (HR, 2.12; 95% CI, 1.61-2.80; P < 0.001) and platelet engraftment (HR, 1.96; 95% CI, 1.39-2.76; P < 0.001) were observed in the PTCy-haplo group. In subgroup analysis, uCBT was associated with improved RFS in AML with poor cytogenetic risk (HR for PTCy-haplo versus uCBT, 2.49; 95% CI, 1.04-5.97; P for interaction = 0.032). In conclusion, survival outcomes were comparable between PTCy-haplo and uCBT in patients with MRD-positive AML. PTCy-haplo was associated with a lower risk of aGVHD, a higher risk of cGVHD and superior hematopoietic engraftment. In the subgroup of patients with poor cytogenetic risk, uCBT was associated with improved RFS.