Liver Transplant Survival Index for Patients with Model for End-Stage Liver Disease Score ≥ 35: Modeling Risk and Adjusting Expectations in the Share 35 Era

Background: The Share 35 policy for liver allocation prioritizes patients with Model for End-Stage Liver Disease (MELD) scores ≥ 35 for regional sharing of liver allografts. To better assess donor-recipient interactions and inform expectations, this study identified factors affecting graft survival independent of MELD score and derived a risk index for transplantation in the MELD ≥ 35 population. Study Design: The United Network for Organ Sharing (UNOS) STAR database was evaluated for deceased donor liver transplants with recipients' MELD ≥ 35, between January 2006 and June 2016. Data were randomly split into test and validate cohorts. Four individual models of graft survival spanning 90 days to 5 years were evaluated with univariate and multivariate Cox proportional hazards analyses against donor- and recipient-specific characteristics. Significant factors were compiled to generate the Liver Transplant Survival Index (LTSI-35), and survival analyses were performed. Results: Five risk groups (very low, low, moderate, high, and severe) were identified, with 1-year graft survival rates of 90.8% ± 0.2%, 89.3% ± 0.3%, 85.0% ± 0.3%, 79.8% ± 0.3%, and 70.3% ± 0.4% (p < 0.001 across groups), respectively. The greatest risk of graft loss was associated with donation after circulatory death (DCD) donors (1-year hazard ratio [HR] = 1.61 [95% CI 1.26 to 2.05], p = 0.001), recipients' requiring ventilator support (HR 1.32 [95% CI 1.17 to 1.51], p < 0.001), and recipient portal vein thrombosis (HR 1.21 [95% CI 1.03 to 1.42], p = 0.003). Subgroup analysis revealed increased risk of graft loss with graft macrosteatosis ≥ 30% on pre-donation biopsy at 90 days (HR 1.64 [1.33 to 1.99], p < 0.001). Conclusions: The LTSI-35 identifies risk factors for graft loss in a high-MELD population which, when combined, may portend worse outcomes. The LTSI-35 may be used to influence donor selection, organ allocation, and to inform expectations for allograft survival.