A novel waitlist dropout score for hepatocellular carcinoma - identifying a threshold that predicts worse post-transplant survival.
It has been suggested that patients with hepatocellular carcinoma (HCC) at high risk of waitlist dropout would have done poorly after liver transplantation (LT) due to tumor aggressiveness. To test this hypothesis, we analyzed risk of waitlist dropout among HCC patients in long wait regions (LWR) to create a dropout risk score, and applied this score in short (SWR) and mid wait regions (MWR) to evaluate post-LT outcomes. We sought to identify a threshold in dropout risk that predicts worse post-LT outcome.Using the UNOS database including all patients with T2 HCC receiving priority listing from 2010-2014, a dropout risk score was created from a developmental cohort of 2,092 LWR patients, and tested in a validation cohort of 1,735 SWR and 2,894 MWR patients.On multivariable analysis, 1 tumor 3.1-5 cm or 2-3 tumors, AFP >20 ng/ml, and increasing Child-Pugh and MELD-Na scores significantly predicted waitlist dropout. A dropout risk score using these four variables (C-statistic 0.74) was able to stratify 1-year cumulative incidence of dropout from 7.1% with a score <7 to 39.5% with a score >23. Patients with a dropout risk score >30 had 5-year post-LT survival of 60.1% versus 71.8% for those with a score <30 (p=0.004). There were no significant differences in post-LT survival below this threshold.This study provided evidence that HCC patients with the highest dropout risk have aggressive tumor biology that would also result in poor post-LT outcomes when transplanted quickly. Below this threshold risk score of <30, priority status for organ allocation could be stratified based on the predicted risks of waitlist dropout without significant differences in post-LT survival.