Graft-versus-host disease and relapse/rejection-free survival after allogeneic transplantation for idiopathic severe aplastic anemia: a comprehensive analysis from the SAAWP of the EBMT.

Survival after Allo-HSCT for severe idiopathic aplastic anemia (SAA) has improved in recent years, approaching 75% at 5 years. However, an SAA-adapted composite endpoint, GVHD and relapse/rejection-free survival (GRFS), may more accurately assess patient outcomes beyond survival. We analyzed GRFS to identify risk factors and specific causes of GRFS failure. Our retrospective analysis from the SAAWP of the EBMT included 479 patients with idiopathic SAA who underwent Allo-HSCT in 2 conventional situations: i) upfront Allo-HSCT from a matched related donor (MRD) (upfront cohort), and ii) Allo-HSCT for relapsed or refractory SAA (rel/ref cohort). Relevant events for GRFS calculation included graft failure, grade 3-4 acute GVHD, extensive chronic GVHD, and death. In the upfront cohort (n=209), 5-year GRFS was 77%. Late Allo-HSCT (i.e., >6 months after SAA diagnosis) was the main poor prognostic factor, specifically increasing the risk of death as the cause of GRFS failure (HR: 4.08, 95% CI [1.41-11.83], p=0.010). In the rel/ref cohort (n=270), 5-year GRFS was 61%. Age was the main factor significantly increasing the risk of death (HR: 1.04, 95% CI [1.02-1.06], p<0.001), acute GVHD (HR: 1.03, 95% CI [1.00-1.07], p=0.041), and chronic GVHD (HR: 1.04 95% CI [1.01-1.08], p=0.032) as the cause of GRFS failure. GRFS after upfront MRD Allo-HSCT was very good, notably with early Allo-HSCT, confirming that younger patients with a MRD should be transplanted immediately. GRFS was worse in cases of salvage Allo-HSCT, most notably in older patients, questioning the utility of Allo-HSCT earlier in the disease course.