Downstaging of advanced hepatocellular carcinoma followed by liver transplantation using immune checkpoint inhibitors: Where do we stand?

Liver transplantation (LT) in patients with hepatocellular carcinoma (HCC) and chronic liver disease (CLD) is limited by factors such as tumor size, number, portal venous or hepatic venous invasion and extrahepatic disease. Although previously established criteria, such as Milan or UCSF, have been relaxed globally to accommodate more potential recipients with comparable 5-year outcomes, there is still a subset of the population that has advanced HCC with or without portal vein tumor thrombosis without detectable extrahepatic spread who do not qualify or are unable to be downstaged by conventional methods and do not qualify for liver transplantation. Immune checkpoint inhibitors (ICI) such as atezolizumab, pembrolizumab, or nivolumab have given hope to this group of patients. We completed a comprehensive literature review using PubMed, Google Scholar, reference citation analysis, and CrossRef. The search utilized keywords such as 'liver transplant', 'HCC', 'hepatocellular carcinoma', 'immune checkpoint inhibitors', 'ICI', 'atezolizumab', and 'nivolumab'. Several case reports have documented successful downstaging of HCC using the atezolizumab/bevacizumab combination prior to LT, with acceptable early outcomes comparable to other criteria. Adverse effects of ICI have also been reported during the perioperative period. In such cases, a 1.5-month interval between ICI therapy and LT has been suggested. Overall, the results of downstaging using combination immunotherapy were encouraging and promising. Early reports suggested a potential ray of hope for patients with CLD and advanced HCC, especially those with multifocal HCC or branch portal venous tumor thrombosis. However, prospective studies and further experience will reveal the optimal dosage, duration, and timing prior to LT and evaluate both short- and long-term outcomes in terms of rejection, infection, recurrence rates, and survival.