The Response Evaluation Criteria in Solid Tumors (RECIST) is inappropriate to assess the direct effects of treatment on hepatocellular carcinoma (HCC) by locoregional therapies such as radiofrequency ablation (RFA) and transarterial chemoembolization (TACE). Therefore, establishment of response evaluation criteria solely devoted to HCC is needed urgently in clinical practice as well as in clinical trials of HCC treatment, such as molecular-targeted therapies, which cause necrosis of the tumor. The Response Evaluation Criteria in Cancer of the Liver (RECICL) was revised in 2015 by the Liver Cancer Study Group of Japan based on the 2009 version of RECICL, which was commonly used in Japan. Major revised points of the RECICL 2015 is to define the target lesions of two lesions per organ or three lesions per liver, up to a maximum of five lesions. The second revised point is that setting the timing at which the overall treatment response has been changed. The third point is that the definition of treatment effect 1 has been changed to more than 50% tumor enlargement, excluding the area of necrosis after treatment. Overall evaluation of treatment response has been amended to make it possible to evaluate the overall response including extrahepatic lesions by systemic therapy, which is similar to RECIST or modified RECIST. We hope this new treatment response criteria, RECICL, proposed by the Liver Cancer Study Group of Japan will benefit HCC treatment response evaluation in the setting of daily clinical practice and clinical trials, not only in Japan, but also internationally.
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