Haploidentical Hematopoietic Stem Cell Transplantation with Post-Transplant Cyclophosphamide for Severe Aplastic Anemia

Severe aplastic anemia is a life-threatening disease usually treated with immunosuppression or HSCT. This is a multicenter retrospective study that included 78 patients who have undergone haploidentical HSCT with PTCy for severe aplastic anemia in Brazil between 2010 and 2019. Median age was 14 y/o (range: 1-69), and most patients had been heavily transfused. Conditioning regimen was FluCyTBI-based, and GVHD prophylaxis consisted of PTCy, MMF, and tacrolimus (13%) or cyclosporine (87%). Most grafts (92%) were bone marrow. One-year OS was 81%, and it was lower in females (HR=4.6; P=0.007) and in those who had graft failure or poor graft function (HR=10.3; P 30 y/o and lower TNC dose. In conclusion, we have shown that haploidentical transplantation for SAA is feasible. The incidence of graft failure/poor graft function was high, and increasing the TBI dose to 300-400 cGy or Cy to 50 mg/kg in the conditioning regimen may overcome graft failure, but not the addition of ATG. Patients who had not been previously exposed to ATG or alemtuzumab might be at high risk of graft failure. High cellular bone marrow grafts should be pursued.