LR-TR viable as an early imaging indicator of local recurrence after radiofrequency ablation for hepatocellular carcinoma: a longitudinal assessment using LI-RADS nonradiation TRA version 2024.

PURPOSE: To evaluate longitudinal changes of LR-TR Viable observations after radiofrequency ablation (RFA) and characterize their temporal relationship with fulfillment of operational imaging criteria for local recurrence of HCC. MATERIALS AND METHODS: This single-institution retrospective study enrolled treatment-naïve HCC patients who underwent RFA as first-line treatment between 2017 and 2024. Baseline HCC was diagnosed by LR-4/LR-5 categorization according to the LI-RADS CT/MRI Diagnostic Algorithm Version 2018 (LI-RADS Diagnostic v2018) in at-risk patients or by histopathology. Two radiologists chronologically reviewed post-RFA CT/MRI examinations using the LI-RADS CT/MRI Nonradiation Treatment Response Algorithm Version 2024 (LI-RADS Nonradiation TRA v2024) and LI-RADS Diagnostic v2018, with disagreements resolved by a third senior radiologist. An operational imaging endpoint for local recurrence was defined as an ablation-margin assignment of LR-4, LR-5, LR-M, or LR-TIV according to LI-RADS Diagnostic v2018, although this algorithm was originally developed for untreated observations. RESULTS: A total of 127 patients (median age, 68 years [IQR, 61-74 years]; 87 men, 40 women) with 136 HCC lesions were evaluated across 606 post-RFA lesion-level assessments. During follow-up, 70 lesions (51.5%) were categorized as LR-TR Viable at least once; 64 (91.4%) concurrently or subsequently fulfilled the operational imaging criteria for local recurrence. Among these 64 lesions, 21 (32.8%) had not yet met the criteria at initial LR-TR Viable assignment but did so during subsequent follow-up. In these 21 lesions, the median interval to criteria fulfillment was 5.0 months (IQR, 4.4-13.0). Lesions were smaller at initial LR-TR Viable assignment than at the subsequent examination meeting the operational imaging criteria (1.3 cm versus 2.0 cm; p < 0.001). CONCLUSION: LR-TR Viable assignment preceded fulfillment of the operational LI-RADS Diagnostic v2018 imaging criteria for local recurrence in approximately one-third of lesions, with a smaller lesion size at initial assignment than at subsequent criteria fulfillment.