Supplementary Material for: Analyses of Intermediate-Stage Hepatocellular Carcinoma Patients Receiving Transarterial Chemoembolization prior to Designing Clinical Trials

<b><i>Background:</i></b> Intermediate-stage hepatocellular carcinoma (HCC) has a high frequency of recurrence and progression to advanced stage after transarterial chemoembolization (TACE), particularly in patients with high tumor burden. Promising new results from immune checkpoint inhibitors (ICIs) and ICI-based therapies are expected to replace TACE, especially in HCC patients with high tumor burden. <b><i>Aims:</i></b> The present study aimed to evaluate the effectiveness of TACE with a view to design clinical trials comparing TACE and ICIs. <b><i>Methods:</i></b> We retrospectively identified intermediate-stage HCC patients undergoing TACE from our database and subdivided patients into low- and high-burden groups based on three subclassification models using the diameter of the maximum tumor and the number of tumors. Clinical outcomes were compared between low- and high-burden intermediate-stage HCC. <b><i>Results:</i></b> Of 1,161 newly diagnosed HCC patients, 316 were diagnosed with intermediate-stage disease and underwent TACE. The median overall survival from high-burden intermediate-stage disease was not significantly different by clinical course, reaching high tumor burden in all subclassification models. The prognosis of high-burden patients after initial TACE was poor compared with low-burden patients for two models (except for the up-to-seven criteria). In all three models, high-burden patients showed a poor durable response rate (DRR) both ≥3 months and ≥6 months and poor prognosis after TACE. Moreover, patients with confirmed durable response ≥3 months and ≥6 months showed better survival outcomes for high-burden intermediate-stage HCC. <b><i>Conclusions:</i></b> Our results demonstrate the basis for selecting a population that would not benefit from TACE and setting DRR ≥3 months or ≥6 months as alternative endpoints when designing clinical trials comparing TACE and ICIs.