Comparison of Gadoxetic Acid-Enhanced Liver Magnetic Resonance Imaging and Contrast-Enhanced Computed Tomography for the Noninvasive Diagnosis of Hepatocellular Carcinoma

Abstract

Introduction: Magnetic resonance imaging (MRI) has been shown to outperform computed tomography (CT) in diagnosing hepatocellular carcinoma (HCC), although inconsistencies exist across studies. We compared the performance of CT and gadoxetic acid-enhanced MRI in diagnosing HCC according to various guidelines, and to assess the incremental value of a second-line examination. Methods: This retrospective multicenter study included patients at risk of developing HCC with focal liver lesions (FLLs) >= 10 mm. These patients underwent both contrast-enhanced CT and gadoxetic acid-enhanced MRI between January 2015 and June 2018. Four radiologists independently assessed the images using criteria from the Liver Imaging Reporting and Data System (LI-RADS), the Asian Pacific Association for the Study of the Liver (APASL), and the Korean Liver Cancer Association-National Cancer Center (KLCA-NCC) guidelines. The diagnostic performance of CT and MRI was compared across guidelines. Results: In total, 1,590 FLLs (median size, 22.6 mm) were analyzed in 1,455 patients (median age, 59 years; male, 1,101). Sensitivity was higher with MRI than with CT for APASL (89.3% [95% CI: 87.7%, 90.8%] vs. 78.9% [95% CI: 77.0%, 80.8%], respectively) and KLCA-NCC (78.7% [95% CI: 76.7%, 85.0%] vs. 73.7% [95% CI: 71.6%, 75.7%], respectively) (p = 0.002 for both). However, LI-RADS showed lower sensitivity with MRI than with CT (70.6% [95% CI: 68.4%, 72.6%] vs. 74.7% [95% CI: 72.6%, 76.7%], p = 0.002), due to fewer nonperipheral washout. MRI re-categorized 22.4%, 32.2%, and 53.5% of non-HCC observations on CT as HCC with LI-RADS, KLCA-NCC, and APASL, respectively. CT re-classified 30.2%, 29.0%, and 25.8% of non-HCC observations on MRI as HCC with LI-RADS, KLCA-NCC, and APASL, respectively. Conclusion: The added value of gadoxetic acid-enhanced MRI after CT depends on the diagnostic criteria used. Restricting washout timing to the portal venous phase in LI-RADS reduces the sensitivity of gadoxetic acid-enhanced MRI relative to CT. Diagnostic guidelines vary for diagnosing hepatocellular carcinoma (HCC) noninvasively on CT and MRI. Although MRI using gadoxetic acid is known to be more sensitive than CT, the results are inconsistent between the studies. As a result, the added value of second-line examination for inconclusive lesion on the first-line examination is not investigated. The study found that the diagnostic accuracy of these two imaging methods varied depending on which diagnostic criteria used. When following the guidelines from the Asian Pacific Association for the Study of the Liver (APASL) and the Korean Liver Cancer Association (KLCA-NCC), MRI had better sensitivity than CT at diagnosing HCC. However, when using the Liver Imaging Reporting and Data System (LI-RADS) criteria, CT actually had higher sensitivity than MRI at diagnosing HCC. These differences occurred because each guideline has different specific requirements for diagnosing HCC. The study also looked at how useful it was to perform a second-line examination when the first-line examination did not definitively diagnose HCC. The added value of this second-line examination varied by guidelines. When MRI was performed after CT for non-HCC lesions, between 22% and 54% of the non-HCC lesions were newly diagnosed as HCC, depending on which guidelines were used. When CT was performed after MRI, about 25-30% of non-HCC observations were newly categorized as HCC across all guidelines. These findings offer evidence for current guidelines and help us to estimate the anticipated added value of the second-line examination for diagnosing HCC in different clinical scenarios using different imaging modalities and diagnostic criteria.