Effects of major liver allocation policy changes on waitlist outcomes in multivisceral transplantation in the United States

Background: Organ allocation in multivisceral transplant (MVT; liver-intestine, liver-pancreas-intestine) is determined based on their ranking in the liver transplant waitlist. MVT candidates do not usually have high laboratory MELDNa (MELD) score and an exception point is given per the OPTN policy. Currently, their exception point is determined as 10% increase in mortality risk to their MELD score. Since 2013, an exception point of 29 has been applied to MVT candidates with approval by regional review board. As major revisions in liver allocation, Share 35 rule and MELDNa score were implemented in 2013 and 2016. The aim of this study was to evaluate effects of these updates in liver allocation policy on waitlist outcomes in MVT. Methods: We examined adult patients who were registered for liver alone (LTA), liver-kidney (L-K), and MVT between 2011 and 2018 by using the UNOS registry. Registration periods were grouped according to the major revisions of liver allocation; 1) pre-Share 35 period (1/1/2011-6/17/2013), 2) post- Share 35 period (6/18/2013-1/10/2016), 3) MELDNa period (1/11/2016- 3/31/2018). 90-day waitlist mortality in MVT candidates were evaluated in each period in comparison with those in LTA/L-K candidates who had similar MELD score (score categories of 20-28 and 29-34) to exception points for MVT candidates. Risks were adjusted by using Fine-Gray regression model. Results: In MVT candidates, while there was no difference between the pre and post-Share 35 periods (HR, 0.96; P=0.29), 90 day-mortality significantly increased in the MELDNa period compared with that in post-Share 35 period (HR, 1.08; P=0.02). Mortality within 90 days in LTA/L-K candidates with MELD score of 20-28 continued to decrease over periods (hazard ratio [HR], 0.91 and 0.82; P=0.042 and \u3c0.001 for pre vs. post-Share 35 periods and post-Share 35 vs. MELDNa periods). 90 day-mortality in LTA/L-K candidates with MELD score of 29-34 significantly decreased in the MELDNa period compared with the post-Share 35 period (HR, 0.78; P\u3c0.001), whereas there was no difference between the pre and post-Share 35 periods (HR, 0.99; P=0.9). Conclusions: While the recent revisions of liver allocation improved waitlist outcomes in LTA/L-K candidates, MVT candidates did not benefit from them and 90 day-mortality significantly increased in the MELDNa period. Exception point for MVT candidates may need to be reconsidered, given the increased number of high score patients