Reduced-toxicity conditioning regimen with low dose post-transplantation cyclophosphamide and low-dose anti-thymocyte globulin as graft-versus-host disease prophylaxis for haploidentical stem cell transplantation in older patients.

Abstract

We retrospectively analyzed outcomes in 55 patients ≥ 55 years of age with hematologic malignancies treated with fludarabine, cytarabine, busulfan, and low-dose cyclophosphamide as the conditioning regimen between January 1, 2019, and November 30, 2023. Neutrophil engraftment was successful in all patients within 28 days, with 54 patients (98.2%) achieving complete donor chimerism. The cumulative incidence of non-relapse mortality was 0% at 30 days, 7.5% at 100 days, and 19% at 1 year. The cumulative incidence of grade II-IV acute graft-versus-host disease (aGVHD) was 25% (95%CI, 15-38%), whereas that of grade III-IV aGVHD was 9.1% (95% CI, 3.3-19%). The cumulative incidence of extensive chronic graft-versus-host disease at 1 year was 3.6% (95%CI, 0.66-11%). The cumulative incidences of relapse, overall survival, and GVHD-free/relapse-free survival at 1 year were 9.0%, 71.6%, and 67.1%, respectively. An RIC conditioning regimen, including a combination of lower PTCy/ATG as GVHD prophylaxis, followed by haplo-SCT, might be a promising option for appropriately selected older patients.