Haploidentical HCT is viable alternative to matched sibling HCT in patients with AML in CR1

In a large-scale study, researchers compared matched sibling donor vs. haploidentical hematopoietic cell transplantation (HCT) for recipients in first complete remission (CR1) and the results show comparable overall survival, leukemia-free survival, non-relapse mortality, relapse, and grade II-IV acute GVHD. 

Transplants took place between 2008 and 2015. According to data reported the Center for International Blood and Marrow Transplant Research (CIBMTR), all patients with acute myeloid leukemia (AML) were adults in CR1, and the haploidentical related transplants (n=336) were mismatched for ≥2 HLA loci among HLA-A, HLA-B, HLA-C, and HLA-DRB1. All 869 matched sibling donor (MSD) transplant recipients received calcineurin inhibitor–based graft-versus-host disease (GVHD) prophylaxis. 

The haploidentical HCT group included more reduced-intensity conditioning (65% vs. 30%), bone marrow grafts (62% vs. 7%) and African American patients (21% vs. 5%), (all p<0.001) than the MSD HCT group.

In a multivariable analysis, haploidentical and MSD patient groups did not differ significantly in overall survival (p=0.15), leukemia-free survival (p=0.50), non-relapse mortality (p=0.16), relapse (p=0.90), or grade II-IV acute GVHD (p=0.98). 

The haploidentical group had a significantly lower rate of chronic GVHD (hazard ratio, 0.38; 95% confidence interval, 0.30-0.48; p<0.001). Further analysis indicated that the lower GVHD was not associated with an improvement in survival.  Subgroup analyses by conditioning intensity and graft source suggested that the reduced incidence of chronic GVHD in haploidentical HCT is not limited to a specific graft source or conditioning intensity. 

Data from the CIBMTR indicate that this study may not reflect current clinical practices, where adults undergoing haploidentical transplants receive moreperipheral blood stem cell (PBSC) grafts, which have been shown to have increased rates of chronic GVHD than those receiving bone marrow grafts.

The researchers concluded that “haplo-HCT is a viable alternative to MSD in these patients” and that their results support preventing a delay in choosing a suitable donor, especially in ethnic minorities.

Rashidi A, et al., Blood Advances