Selecting patients with hepatocellular carcinoma for liver transplantation: Who should receive priority?

One of the major tenets of fair organ allocation is the equitable access and distribution of organs to candidates regardless of their disease. Because of the great scarcity of available organs, the utilitarianism of the final rule as a measure of normative ethics dictates that organs should be allocated to those patients who will maximize the utility of the grafts in terms of survival after transplantation and have the greatest risk of wait-list dropout, whether this dropout is due to death or other reasons (eg, tumor progression). Patients with hepatocellular carcinoma (HCC) constitute a group of patients who would be poorly served by pure Model for End-Stage Liver Disease (MELD) allocation. In the absence of MELD exception points, patients with HCC would have an increased risk of wait-list dropout, generally because of tumor progression, even though they have a relatively low risk of wait-list mortality due to liver disease. Accordingly, it was determined that the risk of tumor progression, rather than the 3-month risk of death, should be used to adjust the MELD score for these patients. Indeed, the adoption of a risk-based allocation system using MELD exception points has lowered wait-list mortality. With HCC now representing the primary indication for liver transplantation for more than a quarter of all transplants, a careful examination of the prioritization of these patients is mandatory. MELD exception points for HCC were originally granted to patients whose tumor burden was within the so-called Milan criteria (stage T1 or T2). However, single-center data, registry data, and Markov modeling have all indicated that the initial judgments overestimated the risks of tumor progression. Using such data, policymakers have continued to refine the prioritization system for HCC patients. First, it was concluded that patients with stage T1 tumors (single lesion<2 cm) would no longer be assigned exception points because virtually none of these candidates experienced wait-list dropout within 1 year. Second, the number of initial exception points granted to patients with T2 tumors was decreased to 22 points (equivalent to a 15% risk of mortality at 3 months). Additional revisions of the HCC allocation policy are ongoing. Despite these efforts, data continue to suggest that with substantially lower wait-list dropout rates and high transplant rates, HCC patients remain at a marked advantage in comparison with non-HCC patients. In this issue of Liver Transplantation, Mehta et al. identify a specific cohort of HCC patients with T2 tumors whose risk of wait-list dropout is very low. The authors performed a retrospective, single-center analysis of adult HCC patients listed for liver transplantation with MELD exception points. They used a competing risk analysis to calculate cumulative incidence rates of dropout from the wait list between the years 2005 and 2011. The authors found that predictors of dropout due to tumor progression or death included the presence of a 3 to 5 cm solitary tumor versus a <3-cm solitary tumor, the presence of more than 1 tumor, the lack of a complete response to