Abstract
To compare the efficacy and safety of the FABT regimen versus the conventional FCA regimen in patients under 40 years old with aplastic anemia (AA) underwent haploidentical hematopoietic stem cell transplantation (haplo-HSCT). This single-center retrospective study included 75 AA patients under 40 years old who underwent haplo-HSCT between January 2021 and January 2025. Patients were categorized into the Fludarabine-ATG-Busulfan-Thiotepa (FABT) group (n = 25) and the Fludarabine-Cyclophosphamide-ATG (FCA) group (n = 50) based on their conditioning regimen. The FABT regimen featured reduced-dose busulfan, fludarabine, cyclophosphamide, thiotepa, and low-dose anti-thymocyte globulin (ATG), followed by post-transplant cyclophosphamide (PTCy), calcineurin inhibitors, and mycophenolate mofetil for Graft-versus-host disease (GVHD) prophylaxis. Primary endpoints were GVHD-free/relapse-free survival (GRFS) and overall survival (OS). Secondary endpoints included engraftment rates, incidence of acute and chronic GVHD, viral reactivation and treatment response. The 3-year GRFS was significantly higher in the FABT group compared to the FCA group (96% vs. 76%, P = 0.032). The 3-year OS was 96% for FABT and 88% for FCA (P = 0.263). The FABT group demonstrated a significantly higher 1-year complete response (CR) rate (96% vs. 78%, P = 0.021) and a lower 3-year CMV reactivation rate (12% vs. 30%, P = 0.019). No significant differences were observed in engraftment rate, EBV reactivation, or cumulative incidence of acute or chronic GVHD between the two groups. The FABT conditioning regimen demonstrates superior outcomes compared to the FCA regimen in young AA patients underwent haplo-HSCT, characterized by significantly improved GRFS and CR rates, and reduced CMV reactivation, without compromising engraftment or increasing GVHD. This regimen represents a promising therapeutic strategy for this patient population.