SIMAP500: A novel risk score to identify recipients at higher risk of hepatocellular carcinoma recurrence following liver transplantation.

Background: Recurrence of hepatocellular carcinoma (HCC) following liver transplantation (LT) has a devastating influence on recipients' survival; however, the risk of recurrence is not routinely stratified. Risk stratification is vital with a long LT waiting time, as that could influence the recurrence despite strict listing criteria.

Aim: This study aims to identify predictors of recurrence and develop a novel risk prediction score to forecast HCC recurrence following LT.

Methods: A retrospective review of LT for HCC recipients at University Hospitals Birmingham between July 2011 and February 2020. Univariate and multivariate analyses were performed to identify recurrence predictors, based on which the novel SIMAP500 (satellite nodules, increase in size, microvascular invasion, AFP > 500, poor differentiation) risk score was proposed.

Results: 234 LTs for HCC were performed with a median follow-up of 5.3 years. Recurrence developed in 25 patients (10.7%). On univariate analyses, RETREAT score > 3, α-fetoprotein (AFP) at listing 100-500 and > 500, bridging, increased tumour size between imaging at the listing time and explant histology, increase in the size of viable tumour between listing and explant, presence of satellite nodules, micro- and macrovascular invasion on explant and poor differentiation of tumours were significantly associated with recurrence, based on which, the SIMAP500 risk score is proposed. The SIMAP500 demonstrated an excellent predictive ability (c-index = 0.803) and outperformed the RETREAT score (c-index = 0.73). SIMAP500 is indicative of the time to disease recurrence.

Conclusion: SIMAP500 risk score identifies the LT recipients at risk of HCC recurrence. Risk stratification allows patient-centric post-transplant surveillance programs. Further validation of the score is recommended.