Incorporation of Ancillary MRI Features Into the LI-RADS Treatment Response Algorithm: Impact on Diagnostic Performance After Locoregional Treatment of Hepatocellular Carcinoma.

The LI-RADS treatment response algorithm may lack sufficient sensitivity for viable tumor after locoregional treatment (LRT) for hepatocellular carcinoma (HCC). The purpose of our study was to evaluate the impact of incorporation of ancillary MRI features on the diagnostic performance of the LI-RADS treatment response algorithm after LRT for HCC. This retrospective study included 141 patients (114 men, 27 women; median age, 56 years) who underwent gadoxetic acid-enhanced MRI after LRT for HCC between October 2005 and January 2020 and subsequent liver surgery. Two readers assessed lesions for LI-RADS features of viability for ancillary MRI features (transitional phase [TP] hypointensity, hepatobiliary phase [HBP] hypointensity, DWI hyperintensity or low ADC, and mild-to-moderate T2 hyperintensity). Interobserver agreement was assessed before reaching consensus. Significant ancillary features were identified using random forest analysis. The impact of incorporation of significant ancillary features on diagnostic performance for incomplete pathologic necrosis (IPN; pathologically viable tumor > 0 mm) was assessed using McNemar tests. Complete pathologic necrosis (CPN) was observed in 88 of 181 (48.6%) lesions. Interreader agreement was almost perfect for LI-RADS features of viability (κ = 0.92-0.97) and was substantial to almost perfect for ancillary features (κ = 0.73-0.94). Random forest analysis identified TP hypointensity (present in 8.0%, 25.0%, and 75.3% of lesions with CPN, viable tumor < 10 mm, and viable tumor ≥ 10 mm, respectively) and HBP hypointensity (9.2%, 25.0%, and 74.0%, respectively) as significant ancillary features. For detecting IPN, LR-TR (treatment response) Viable or LR-TR Equivocal had higher sensitivity than LR-TR Viable (71.0% vs 57.0%, respectively; = .001) but had lower specificity (86.4% vs 94.3%, = .02). However, LR-TR Viable or LR-TR Equivocal and TP hypointensity showed higher sensitivity than LR-TR Viable (64.5% vs 57.0%, = .02) without a significantly different specificity (90.9% vs 94.3%, = .25). LR-TR Viable or LR-TR Equivocal and HBP hypointensity also showed higher sensitivity than LR-TR Viable (65.6% vs 57.0%, = .01) without a significantly different specificity (90.8% vs 94.3%, = .25). TP hypointensity and HBP hypointensity increase the sensitivity of LI-RADS treatment response algorithm for viable tumor without lowering specificity. The two identified ancillary features may improve tumor viability assessment and planning of additional therapies after LRT for HCC.