Tumor response evaluation criteria for HCC (hepatocellular carcinoma) treated using TACE (transcatheter arterial chemoembolization): RECIST (response evaluation criteria in solid tumors) version 1.1 and mRECIST (modified RECIST): JIVROSG-0602

BACKGROUND Two standard sets of criteria are used to evaluate the tumor response of hepatocellular carcinoma (HCC): RECIST (Response Evaluation Criteria in Solid Tumors) and modified RECIST (mRECIST). The purpose was to compare two tumor response evaluation criteria, RECIST version 1.1 and mRECIST, for HCC treated using transcatheter arterial chemoembolization (TACE). METHODS The radiological findings of patients who underwent TACE for HCCs in a multicenter clinical trial were examined. Sixty-five lesions in 21 patients treated with TACE without mixing iodized-oil were evaluated. The tumor size was evaluated by measuring the entire lesion, including the necrotic part, using RECIST version 1.1, whereas only the contrast-enhanced part observed during the arterial phase was measured using mRECIST. Five radiologists independently measured each lesion twice. To evaluate the inter-criteria reproducibility, the complete response (CR) rate, the response rate, the kappa statistics, and the proportion of agreement (PA) for response categories were calculated. The same analyses were conducted for inter- and intra-observer reproducibility. RESULTS In the inter-criteria reproducibility study, the CR rate and the response rate obtained using mRECIST (56.9% and 79.7%) were higher than those obtained using RECIST version 1.1 (9.2% and 43.1%). In the inter- and intra-observer reproducibility study, mRECIST exhibited an 'almost perfect agreement', while RECIST version 1.1 exhibited a 'substantial agreement'. CONCLUSIONS Considerable differences in the CR rate and the response rate were observed. From the viewpoint of the high inter- and intra-observer reproducibility, mRECIST may be more suitable for tumor response criteria in clinical trials of TACE for HCC.