LI-RADS CT/MRI Radiation Treatment Response Assessment Version 2024: Category Redistribution and Short-Term Outcomes...

BACKGROUND. LI-RADS CT/MRI Radiation Treatment Response Assessment (TRA) algorithm version 2024 (v2024) addresses a pitfall of the earlier algorithm that relates to the expected persistent enhancement of hepatocellular carcinoma (HCC) responding to radiation. v2024 removes LR-TR Equivocal, introduces LR-TR Nonprogressing (stable or decreasing masslike enhancement), and more narrowly defines LR-TR Viable (new or increasing masslike enhancement). OBJECTIVE. The purpose of this study was to evaluate in patients with HCC treated by ⁹⁰Y radioembolization the redistribution of categories in LI-RADS CT/MRI Radiation TRA v2024 compared with LI-RADS CT/MRI TRA version 2018 (v2018) and to assess the short-term outcomes for patients with HCC assessed using v2024 categories. METHODS. This retrospective study included 242 patients (57 women and 185 men; median age, 65 years) with 319 HCCs treated by ⁹⁰Y radioembolization from February 2011 to March 2022 and evaluated by initial 3-month posttreatment CT or MRI examinations. Two radiologists assigned v2018 and v2024 categories; a third radiologist resolved discrepancies. The radiologists also assessed available second posttreatment CT or MRI examinations by use of v2024. Overall survival (OS) was determined. RESULTS. On initial follow-up, by use of v2018, 18 lesions (5.6%) were LR-TR Nonviable, 21 (6.6%) were LR-TR Equivocal, and 280 (87.8%) were LR-TR Viable; by use of v2024, 18 (5.6%) were LR-TR Nonviable, 182 (57.1%) were LR-TR Nonprogressing, and 119 (37.3%) were LR-TR Viable. All LR-TR Equivocal and 161 LR-TR Viable lesions (57.5%) categorized by v2018 were recategorized as LR-TR Nonprogressing by v2024. Of 96 LR-TR Nonprogressing lesions with second follow-up, 63 (65.6%) remained LR-TR Nonprogressing, 19 (19.8%) transitioned to LR-TR Nonviable, and 14 (14.6%) transitioned to LR-TR Viable. Of 29 LR-TR Viable lesions categorized by use of v2024 that had second follow-up, 23 (79.3%) remained LR-TR Viable, and six (20.7%) transitioned to LR-TR Nonprogressing. By Kaplan-Meier analysis using initial categories, OS showed no significant difference between LR-TR Equivocal and LR-TR Viable for v2018 (p = .05) but was significantly worse for LR-TR Viable than LR-TR Nonprogressing for v2024 (p < .001). CONCLUSION. LR-TR Viable was substantially less frequent for v2024 than for v2018, and the majority of lesions were assigned to the LR-TR Nonprogressing category. Using v2024, most LR-TR Viable lesions and the majority of LR-TR Nonprogressing lesions on initial follow-up remained as such on later imaging. Initial v2024 categories were associated with OS. CLINICAL IMPACT. The findings support the revisions in v2024.