Therefore, in this study, we analyzed (a) the prevalence of unresectable HCC with iso-high intensity in the hepatobiliary phase of EOB-MRI in patients with unresectable HCC who were treated with lenvatinib, (b) the response to lenvatinib, and (c) the relationship between the presence of unresectable HCC with iso-high intensity in the hepatobiliary phase of EOB-MRI and β-Catenin (CTNNB-1) mutations determined by a cfDNA analysis. The gene discussed is CTNNB1; the disease is hepatocellular carcinoma.