Fairness of liver graft allocation under current HCC MELD score exception policy in Hong Kong

Abstract

OBJECTIVE: This study is to determine whether liver transplant waitlist candidates with hepatocellular carcinoma (HCC) are over-advantaged against the non-HCC candidates for graft allocation under current HCC prioritization scheme. BACKGROUND: The priority of liver graft access in Hong Kong is ranked by candidates’ Model of End-stage Liver Disease (MELD) scores. MELD score was originally developed to model the survival of patients with decompensated cirrhosis, it is unable to reflect the risk of mortality in candidates listed for indications other than liver failure, such as hepatocellular carcinoma, who has relatively preserved liver function. In an attempt to fairly represent the urgency of need for liver transplant in these candidates, a prioritization scheme to assign a MELD score bonus is implemented. In Hong Kong, HCC candidates with T2 disease receive 18 MELD score points if the tumor remained in T2 after an observation period of 6 months. An increment of 2 MELD score points is given for every 3 months without disease progression. There is concern that such a scheme would over-prioritize graft allocation to HCC candidates. METHOD: Waitlist information and status of candidates listed during the period 1/10/2009–14/8/2015 is retrieved from the Hong Kong Organ Registry & Transplant System to calculate the waitlist outcomes (liver transplant, dropout, removal, alive waiting) for HCC and non-HCC candidates. All adult candidates over the age of 18 listed for all indications are included. Waitlist outcomes are compared between candidates with and without HCC. Student’s t test is used to compare between means. z-score test is used to compared between proportions. Person correlation test is used for determine correlation between continuous linear variables. RESULT: One hundred and forty-one HCC candidates is compared with 289 non-HCC candidates. Eighty-eight (62%) HCC candidates received MELD exception score of 18 or above. Significantly higher proportion of HCC candidates with MELD exception received liver transplant during the period compared to non-HCC candidates (60.3% vs. 45%, p = 0.01); while there is no significant different in dropout rate between HCC and non-HCC candidates (25% vs. 28.4%, p = 0.5). Further analysis showed that seasonal variation in graft supply is weakly but significantly correlated to dropout rate of non-HCC candidates but not to that of HCC candidates (R2 = 0.336, p = 0.003 vs. R2 = 0.08, p = 0.181). CONCLUSION: HCC candidates with MELD exception are over-advantaged in liver graft allocation under the current prioritization scheme.