Comparing the Prognostic Value of Quantitative Response Assessment Tools and LIRADS Treatment Response Algorithm in Patients with Hepatocellular Carcinoma Following Interstitial High-Dose-Rate Brachytherapy and Conventional Transarterial Chemoemboliz

<b>Background/Objectives:</b> The aim of this study was to investigate the prognostic value of established response assessment tools for hepatocellular carcinoma (HCC) treated with high-dose-rate interstitial brachytherapy (iBT) alone or with transarterial chemoembolization (cTACE). <b>Methods:</b> (Non-)responders were categorized using size-based RECIST 1.1 and WHO criteria, enhancement-based mRECIST and EASL criteria, and the LI-RADS Treatment Response Algorithm (LR-TRA). The outcomes were the overall survival (OS), progression-free survival (PFS), and time to progression (TTP). The statistics used included Fisher's exact test, a <i>t</i>-test, the Mann-Whitney-U test, and a Kaplan-Meier analysis. The median OS, PFS, and TTP were higher in patients following iBT (26.3, 9.1, and 13.0 months) than following cTACE/iBT (23.3, 7.6, and 9.2 months). <b>Results:</b> The enhancement-based criteria identified more responders and predicted PFS and TTP better compared to the size-based criteria. At two months, the cTACE/iBT responders showed improved PFS (mRECIST and EASL: 11.3 vs. 2.3 and 11.0 vs. 2.3, <i>p</i> < 0.01) and TTP (mRECIST and EASL: 11.9 vs. 2.4 months, <i>p</i> < 0.01) by the enhancement-based criteria. An EASL assessment at five months predicted improved survival following both cTACE/iBT (PFS: 11.9 vs. 5.1 months, <i>p</i> = 0.03; TTP: 12.4 vs. 5.0, <i>p</i> < 0.01) and iBT (11.1 vs. 5.1 months, <i>p</i> = 0.04; 13.0 vs. 5.3, <i>p</i> < 0.01). The LR-TRA showed OS benefits at five months for cTACE/iBT responders. Size-based criteria were not prognostic. <b>Conclusions:</b> Extending follow-up post-iBT or post-iBT/cTACE may improve responder stratification and prognostication.