Introduction: Severe Aplastic Anemia (SAA) is a life-threatening hematopoietic stem cell disorder; Allogeneic hematopoietic stem cell transplantation (HSCT) offers potential cure for severe aplastic anemia (SAA). Long-term outcomes are significantly impacted by graft failure and graft-versus-host disease (GVHD). We analyzed a single-center cohort of SAA patients undergoing HSCT, focusing on the composite outcome of GVHD and relapse/rejection-free survival (GRFS) to evaluate patient outcomes beyond overall survival (OS).

Methods: We reported a novel composite endpoint of GVHD-free/relapse -free survival (GRFS) in patients with refractory and treatment naïve SAA who underwent HSCT at our center between Nov 2004 to October 2024. GRFS is defined as being alive without aplastic anemia , acute GvHD (aGvHD) grades III/ IV, extensive chronic GvHD (cGvHD), and graft loss in patients with SAA. We compared outcomes by donor type (matched related donor [MRD] vs Haplo identical donor).

Results: Total of 118 patients with SAA; the median time from diagnosis to transplant (Dx-Tx) was 3.6 months (range, 0.7-129) and the median follow-up was 48 months (range, 2.1-212). Of these, 25 had failed front-line IST and 93 patients were treatment-naïve (TN). The median age at Tx was 17 years (range, 1.1-61). Donor type was HLA matched related (MRD, n=94), haploidentical (n= 24). One hundred five patients received myeloablative conditioning (MAC); 82 patients received BM as a stem cell source. The median time for neutrophil recovery was 16 days (range 9–40) and platelet recovery was 21 days (range 10–106). The estimated 1-yr OS, EFS, and GRFS were 87.9%, 81%, and 74%, respectively, and the estimated 5-yrs OS, EFS, and GRFS were 85.7%, 69.8%, and 62.7 %, respectively. In univariable analysis factors associated with better outcomes if GRFS used as an endpoint: MRD, BM as stem cell source, no prior ATG based IST. In multivariable analysis, the strongest positive predictor of OS (HR: 2.81; p=0.031, EFS (HR: 3.81; p<0.001), and GRFS (HR: 2.58; p=0.004) was bone marrow as a stem cell source.Conclusion: In severe aplastic anemia, allogeneic HCT produces high long-term survival, but significant post-transplant morbidity persists. At our center, 5-year OS and GRFS were 86% and 63%, respectively. Bone marrow grafts and upfront transplant with no prior ATG based ISI were associated with superior GRFS. These data support continued optimization of donor selection, graft choice as well as timing of Allo-HCT in patients who are lacking MRD to maximize GVHD/relapse-free survival in SAA.

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2025
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