Discussion
aggressive HCC, tumor, HCC, OPTN
TUMOR, HBP
Our study demonstrated that EOB-MRI had an overall superior sensitivity but lower specificity compared to CECT for HCC diagnosis in non-treated LR-4/5 lesions referenced against explant histopathology. EOB-MRI was superior to CECT on analysis by size (< 2 cm versus > 2 cm), although without statistical significance. In the LR-5 category, although EOB-MRI and CECT had statistically similar pooled diagnostic performance without consideration of HCC size, EOB-MRI was inferior to CECT in the < 2 cm subgroup. HCC detection sensitivity and specificity with CECT and EOB-MRI have wide reported variability in the LR-4/5 and LR-5 categories defined by LI-RADSv2018 [Evaluation of whole-liver explant parenchyma has the merit of detecting HCC invisible on imaging, thereby getting truer imaging sensitivity estimates. The ‘real world’ or true sensitivities of EOB-MRI and CECT in LR-4/5 categories were lower in our study when analyses included all HCC diagnosed at explant histopathology irrespective of a corresponding imaging observation. A prior meta-analysis and a recent study have reported lower sensitivities of EOB-MRI in studies wherein liver explant was the only reference standard [HBP signal as an AF for adjusting LI-RADS category significantly improved EOB-MRI sensitivity in LR-4/5 observations in this study, regardless of size and for < 2 cm group, without significant impact on specificity. A prior retrospective study reported no significant differences between CECT and EOB-MRI for HCC diagnosis with LR-4/5 and LR-5 categories [In our study, EOB-MRI was superior to CECT for detection of < 2 cm viable HCC in treated lesions as per LI-RADS TRA. However, without size consideration, there were no significant differences between the two modalities like in some prior studies [In this study, EOB-MRI and CECT had equivalent performances for assessing simulated LT eligibility based on MC with LI-RADSv2018 and OPTN criteria in reference to explant histopathology, even as lower accuracies were observed in prediction of patients exceeding MC. Although recent studies have demonstrated moderate to high accuracy for determining LT eligibility based on MC using CECT and EOB-MRI with LI-RADSv2018 and OPTN, however in these retrospective studies [We must acknowledge some limitations of this study. This was a single-center study with a limited patient cohort; however, all patients were enrolled prospectively, and explant histopathology correlation was available for the entire study cohort. The lack of using threshold growth in this study for assignment of LI-RADS categories may have underestimated the sensitivity for HCC diagnosis but is applicable to both modalities. The mean time interval between CECT and LT was 1 month longer than the time between EOB-MRI and LT, which could have led to changes in HCC characteristics, thereby impacting imaging evaluation variably between CECT and EOB-MRI. We acknowledge that the three-month interval may change tumor size for aggressive HCC, and it would be ideal to have both CECT and EOB-MRI performed closely before LT. However, since we could not predict the exact timepoint of LT, it was not feasible to perform both EOB-MRI and CECT at every 3-month follow-up interval. It can be challenging to precisely match every lesion recorded on imaging to the liver explant, particularly with small lesion size and because of the shrinkage effects of formalin fixation. Lastly, since we used CPN or non-CPN at histopathologic examination as the reference standard for viable HCC in treated lesions, microscopically viable HCC could have led to underestimation of LR-TR viable category.