Simulating the impact of survival benefit-based liver transplant organ allocation

In the United States and much of the world, prioritization for a deceased donor liver transplant focuses on sickest-first, based on allocating organs using the MELD score. There have been calls to instead allocate organs based on transplant survival benefit, but the impact of such a system on the broader waitlist population is unknown.

We performed a simulation study using the Liver Simulated Allocation Model to compare the current US system of liver allocation to the one using different time horizons, focused on pretransplant survival only, posttransplant survival only, and survival benefit (difference of posttransplant survival and pretransplant survival). Changing liver allocation to a survival benefit-based system was simulated to lead to a small improvement in average patient-level posttransplant survival (mean survival over a 5-year time horizon of 4.24 y vs. 4.19 y in the current system). However, this small improvement was associated with a simulated decrease in transplants and an increase in waitlist mortality of 400 deaths per year. The resulting net benefit overall (pretransplant deaths and posttransplant survival) was negligible under a survival benefit-based allocation approach.

Our simulations predicted that survival benefit-based allocation would only increase posttransplant survival by an average of 18 days per recipient at the expense of a simulated increase in waitlist mortality of 400 deaths per year. In the current practice of liver transplantation, with the sickest-first allocation operating in a system where transplant physicians ration organs to maximize outcomes, the overall survival benefit is maintained and not compromised.