Outcomes of Haploidentical Stem Cell Transplantation using Total Body Irradiation (600 cGy) and Fludarabine with Antithymocyte Globulin in Adult Patients with Severe Aplastic Anemia: A Prospective Phase II Study

The aim of this study was to verify the feasibility of rabbit antithymocyte globulin (ATG; 5 mg/kg) in combination with 600 cGy of fractionated total body irradiation (fTBI; 3 doses of 200 cGy) and fludarabine (Flu; 150 mg/m²) as a conditioning regimen for haploidentical stem cell transplantation from a related mismatched donor (haplo-SCT) in adult patients with severe aplastic anemia (SAA). We analyzed 47 consecutive patients who underwent haplo-SCT, including 24 patients from our previous pilot report. The median age was 36.0 years (range, 17 to 61 years), and 25 patients (53%) were very severe aplastic anemia (VSAA) at transplantation. All patients achieved primary engraftment. The cumulative incidence of grade ≥II acute graft-versus-host disease (GVHD) and chronic moderate or greater GVHD was 27.7% at 100 days and 13.5% at 3 years, respectively. With a median follow-up of 32.3 months, the 3-year probability of overall survival and failure-free survival was 91.0% and 88.6%, respectively. The 3-year GVHD- and failure-free survival (GFFS) was 71.6%. Offspring donor and lower comorbidity index were independent factors correlated with higher GFFS in multivariate analysis. In conclusion, the outcomes of haplo-SCT with fTBI 600 cGy/Flu/ATG-5 indicate that haplo-SCT can be an effective alternative option when a fully matched donor is not available or a patient with VSAA needs an urgent transplantation.