Haploidentical vs. sibling, unrelated, or cord blood hematopoietic cell transplantation for acute lymphoblastic leukemia.

The role of haploidentical hematopoietic cell transplantation (HCT) using post-transplant cyclophosphamide (PTCy) for acute lymphoblastic leukemia (ALL) is being defined. We performed a retrospective, multivariate analysis comparing outcomes of HCT approaches by donor for adults with ALL in remission. The primary objective was to compare overall survival (OS) between haploidentical HCT using PTCy and HLA-matched sibling donor (MSD), 8/8 HLA-matched unrelated donor (MUD) , 7/8 HLA-matched UD, or umbilical cord blood (UCB) HCT. Comparing haploidentical to MSD HCT, OS, leukemia-free survival (LFS), non-relapse mortality (NRM), relapse, and acute graft-versus-host disease (aGVHD) were not different but chronic GVHD (cGVHD) was higher with MSD HCT. Compared to MUD HCT, OS, LFS, and relapse were not different but MUD HCT had increased NRM (HR 1.42, P=0.02), grade 3-4 aGVHD (HR 1.59, P=0.005), and cGVHD. Compared to 7/8 UD HCT, LFS and relapse were not different, but 7/8 UD HCT had worse OS (HR 1.38, P=0.01) and increased NRM (HR 2.13, P=<0.001), grade 3-4 aGVHD (HR 1.86, P=0.003), and cGVHD (HR 1.72, P=<0.001). Compared to UCB HCT, late OS , late LFS, relapse, and cGVHD were not different but UCB HCT had worse early OS (≤18 months, HR 1.93, P<0.001), worse early LFS (HR 1.40, P=0.007) and increased incidences of NRM (HR 2.08, P<0.001) and grade 3-4 aGVHD (HR 1.97, P<0.001). Haploidentical HCT using PTCy showed no difference in survival but less GVHD compared to traditional MSD and MUD HCT and is the preferred alternative donor HCT option for adults with ALL in CR.