S2704 Epidemiology and Outcomes of Hepatic Veno-Occlusive Disease in Allogenic Stem Cell Transplant Recipients in the United States

Introduction: Hepatic veno-occlusive disease (HVOD), or sinusoidal obstruction syndrome (SOS), is a potentially life-threatening complication following allogeneic stem cell transplantation (allo-SCT). Historically, HVOD affected up to 60% of allo-SCT recipients, with mortality rates over 75% in severe cases. The approval of defibrotide in 2016 represented a major therapeutic milestone, significantly improving outcomes in high-risk patients. Despite this, large-scale data on HVOD epidemiology and outcomes in allo-SCT recipients remain limited. Methods: We utilized National Inpatient Sample (2016-2020) to examine factors associated with HVOD in allo-SCT recipients. Admissions for allo-SCT and HVOD were identified using ICD 10 codes. Baseline characteristics, including patient demographics, hospital characteristics, comorbidities, complications and outcomes were compared between allo-SCT admissions with and without HVOD. Categorical variables were analyzed by χ² test (%), and continuous variables by adjusted Wald’s test (mean ± SD). Results: During the study period, 200 allo-SCT admissions with HVOD were identified. HVOD admissions were younger (45.05 vs 52.42 years; P = 0.0045) and were more likely to be woman (43.72% vs 25%; P = 0.0191). They had higher rates of acute graft-versus-host disease (GVHD) (17.5% vs 6.47%; P = 0.0043), acute respiratory failure (32.5% vs 8.37%; P < 0.001), and acute kidney injury (50% vs 20.66%; P < 0.001). Hepatic complications, including portal hypertension (7.5% vs 0.52%; P < 0.001), hepatic encephalopathy (12.5% vs 0.28%; P < 0.001), cirrhosis (7.5% vs 0.07%; P < 0.001), ascites (37.5% vs 1.97%; P < 0.001) and spontaneous bacterial peritonitis (2.5% vs 0.06%; P < 0.001) were also more common in this cohort. HVOD was associated with worse outcomes, including longer hospital stays (45.5 vs 29.51 days; P < 0.001) and over 6 times higher in-hospital mortality (30% vs 4.72%; P < 0.001). HVOD also imposed a greater economic burden, with more than double mean total hospitalization charges ($1,321,650 vs $541,391.1; P < 0.001) and nearly triple hospitalization costs ($358,463.2 vs $141,464.1; P < 0.001). Conclusion: This large-scale study shows HVOD in allo-SCT drives severe hepatic complications and multi-organ dysfunction, leading to excessively high (>6×) in-hospital mortality, prolonged hospital stays, and substantially increased (2-3×) healthcare costs. These stark outcomes underscore an urgent need for improved risk stratification models and novel, liver-focused therapeutic strategies.