Abstract No. 83 Survival of Equivocal LI-RADS Post-Treatment Category in Hepatocellular Carcinoma after Transarterial Radioembolization

The 2017 LI-RADS treatment response (LR-TR) algorithm classifies hepatocellular carcinoma (HCC) post-locoregional therapies as non-viable, viable, and equivocal. The equivocal category denotes an uncertain enhancement pattern not aligned with that of viable tumor. The purpose of this study was to evaluate the survival of HCC patients categorized as LR-TR equivocal post-transarterial radioembolization (TARE). This retrospective study consists of HCC patients who underwent TARE at a single institution from 2017-2022. Three post-TARE LR-TR reads were collected. Patients were classified into 3 groups based on LR-TR category of the first scan post-TARE (average 1.4 ± 2.8 months): equivocal, viable, and nonviable. Equivocal patients were further stratified by clinical course based on the third post-TARE read into viable, nonviable, or equivocal. Median survival was compared between groups. 141 patients were examined in the study, with 72 equivocal (51.1%), 25 viable (17.7%), and 44 nonviable (31.2%) post-TARE. Median survival was 2.3 years for equivocal, 1.9 years for viable, and 3.6 years for nonviable (P = 0.10). Of the equivocal patients, 28 were retreated with locoregional therapy (11 TACE, 8 ablations, 9 TARE) 6.8 ± 4.9 months after initial TARE. The clinical course of the equivocal group after the first equivocal scan and following retreatment if necessary was 16 equivocal (22.2%), 11 viable (15.3%), and 45 nonviable (62.5%) (average follow-up time post-TARE 8.7 ± 4.8 months). When stratified by eventual clinical course, median survival of the initial equivocal cohort post-TARE was 2.6 years for equivocal, 3.1 years for viable, and 4.1 years for non-viable (P = 0.13). Characterizing clinical outcomes post-TARE elucidates the implications of an equivocal read. Several equivocal patients post-TARE were retreated with subsequent locoregional therapy, and most were eventually nonviable after 3 post-TARE scans. Of the equivocal patients post-TARE, the patients who remained equivocal had the shortest survival, suggesting that equivocal tumors are potentially more pathologically advanced, complicated to treat, and have difficult-to-interpret enhancement patterns.