Evolution from WHO to EASL and mRECIST for hepatocellular carcinoma: considerations for tumor response assessment

Radiological response assessment criteria in hepatocellular carcinoma (HCC) have evolved to accurately evaluate tumor responses. The WHO criteria and the subsequent Response Evaluation Criteria in Solid Tumors (RECIST) evaluate change in tumor size; however, these criteria generally ignore tumor necrosis and therefore may underestimate treatment responses. Thus, a panel of experts of the European Association for the Study of Liver (EASL) amended the response criteria to take into account tumor necrosis. In 2010, the modified RECIST (mRECIST) was developed, which consider both the concept of tumor viability based on arterial enhancement and single linear summation, ultimately simplifying EASL criteria. Currently, the mRECIST represents the gold standard for radiologically evaluating tumor response during HCC treatment. Here, the authors review application and performance of mRECIST as well as other HCC response assessment criteria and discuss unmet and open issues regarding response evaluation for HCC treatments.