Hepatic sinusoidal obstruction syndrome after allogeneic hematopoietic stem cell transplantation in adult patients with idiopathic aplastic anemia

We retrospectively investigated the incidence, risk factors, and outcomes of SOS (sinusoidal obstruction syndrome; previously veno-occlusive disease [VOD]) after allogeneic hematopoietic stem cell transplantation (alloHSCT) in aplastic anemia. Two hundred and sixty patients were included in the analysis. SOS developed in 7.3% (n=19/260) of patients. Classical Cy (200mg/m²)-ATG was the most common conditioning regimen (84.2%) in the SOS group. The SOS mortality rate was 4/19 (21.1%). Univariate analyses revealed that Cy 200mg/m² conditioning (p=0.035), classical Cy-ATG conditioning (p=0.007), and horse ATG conditioning (p<0.001) were significant risk factors for developing SOS. Multivariate analysis revealed that only horse ATG conditioning was a poor prognostic factor (HR=3.484; 95% CI 1.226-9.904; p=0.002). Rabbit ATG (HR 12.719; 95% CI 2.332-69.373; p=0.003) and weight gain>10% (HR 35.655; 95% CI 2.208-575.805; p=0.012) were risk factors in the overall SOS group. Both rabbit ATG conditioning and weight gain of more than 10% were associated with poor overall survival with a median of 1.2 months (5Y survival rate, any risk factor vs. none: 74.6% vs. 0.0%; p<0.001; Fig. 2) in the SOS group. In conclusion, SOS is a relatively rare (7.3%) but highly fatal (21.1%) acute complication of alloHSCT in AA, and the horse ATG conditioning regimen was a significant risk factor for developing SOS.