Safety and Efficacy of Haploidentical Peripheral Blood Stem Cell Transplantation for Myeloid Malignancies Using Post-transplantation Cyclophosphamide and Anti-thymocyte Globulin as Graft-versus-Host Disease Prophylaxis

Haploidentical stem cell transplantation (haploSCT) has greatly improved access to curative treatment for myeloid malignancies in patients without suitable matched sibling/unrelated donors. We investigated the safety and efficacy of haploSCT after reduced intensity conditioning (RIC) with anti-thymocyte globulin (ATG), post-transplant cyclophosphamide (PTCy), and cyclosporine to prevent rejection and graft-versus-host disease (GVHD). In this study, 47 patients received RIC using fludarabine, busulfan, and total body irradiation (200 cGy). Unmanipulated peripheral blood grafts were used. GVHD prophylaxis included ATG (4.5 mg/kg day–3 to −1), PTCy (50 mg/kg/day day +3, +4), and cyclosporine from day +5. The median follow-up was 15 months (range 3–27). Thirty one (66%) patients had acute myeloid leukemia (AML), 10 (21%) had high-risk myelodysplastic syndrome, and 6 (13%) had a myeloproliferative neoplasia. Median age was 60 years (range 22–73). The d+100 cumulative incidences of grade II–IV and III–IV acute GVHD were 17% (95% confidence interval (CI) 7.9–29.1) and 6.4% (1.6–15.9), respectively. The cumulative incidence of moderate-severe chronic GVHD at 1 year was 15.2% (95% CI 6.5–27.1). Overall survival (OS) and relapse-free survival (RFS) were 55.2% (95% CI 39.5–68.4) and 49.5% (95% CI 34.2–63), respectively. Nonrelapse mortality (NRM) for all patients at 1 year was 37.1% (95% CI 23.2–51.1). Infection was the main cause of death (26%). For AML, 1-year OS, RFS, and NRM were 64.1% (95% CI 43.3–78.9), 54.5 (95% CI 34.6–70.7), and 26.8% (95% CI 12.3–43.6), respectively. In conclusion, unmanipulated haploidentical peripheral blood stem cells (PBSC) transplantation following RIC and dual in vivo T-cell depletion results in a low incidence of acute and chronic GVHD for patients diagnosed with myeloid malignancies.