Posttransplant Cyclophosphamide‐Based Haploidentical Transplantation, With MMF 30 mg/kg, Compared With Unrelated Donor Transplantation With ATG 6 mg/kg, With Bone Marrow or Peripheral Blood Stem Cell Grafts

Several adaptations have been reported since the introduction of posttransplant cyclophosphamide (PTCy)‐based haploidentical transplantation (Haplo). This single‐center observational study compared the outcomes of PTCy‐based Haplo with MMF at 30 mg/kg to a concurrent cohort of unrelated donors (URD) who received mainly ATG at 6 mg/kg proximal to transplantation. We included 174 patients (median follow‐up: 33 months). Two‐year OS for Haplo was 55%, which was not significantly lower than that for URD (67%, p = 0.22). Two‐year RFS was 53% for Haplo, compared to 60% for URD ( p = 0.31). Two‐year GRFS was significantly worse for Haplo (24%) compared to URD (40%, p < 0.01). Relapse rates were similar (16% for Haplo and 21% for URD, p = 0.66), but non‐relapse mortality was significantly higher for Haplo (31%) versus 19% for URD ( p = 0.04). GVHD outcomes did not differ in univariable analyses. In multivariable analyses, there was a trend toward higher grades III–IV aGVHD (HR = 2.01, p = 0.08) and moderate to severe cGVHD (HR = 1.80, p = 0.05). In summary, we have shown that MMF at 30 mg/kg in Haplo transplants achieved similar PFS and OS compared to ATG‐based URD. However, GRFS was lower, likely due to a significantly higher NRM associated with a trend towards higher moderate to severe cGVHD.