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

Background & Aims: In the US, 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. Approach & Results: We performed a simulation study using the Liver Simulated Allocation Model (LSAM) to compare the current US system of liver allocation to one, using different time horizons, focused on: pre-transplant survival only, post-transplant survival only, and survival benefit (difference of post-transplant survival and pre-transplant survival). Changing liver allocation to a survival benefit-based system was simulated to lead to a small improvement in average patient-level post-transplant survival (mean survival over 5-year time horizon of 4.24 y vs. 4.19 y in 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 (pre-transplant deaths and post-transplant survival) was negligible under a survival benefit-based allocation approach. Conclusions: Our simulations predicted that survival benefit-based allocation would only increase post-transplant survival by an average of 18 days per recipient, at the expense of a simulated increase in waitlist mortality of 400 deaths per year. The current practice of liver transplantation, with sickest-first allocation operating in a system where transplant physicians ration organs to maximize outcomes, survival benefit overall is maintained and not compromised.