Non-enhanced magnetic resonance imaging as a surveillance tool for hepatocellular carcinoma: Comparison with ultrasound

Abstract

Background & aims: Recently revised international guidelines for hepatocellular carcinoma (HCC) suggest that patients with inadequate ultrasonography be assessed by alternative imaging modalities. Non-enhanced MRI has potential as a surveillance tool based on the short scan times required and the absence of contrast agent-associated risks. This study compared the performance of non-enhanced MRI and ultrasonography for HCC surveillance in high-risk patients.

Methods: We included 382 high-risk patients in a prospective cohort who underwent 1 to 3 rounds of paired gadoxetic acid-enhanced MRI and ultrasonography. Non-enhanced MRI, consisting of diffusion-weighted imaging (DWI) and T2-weighted imaging, was simulated and retrospectively analyzed, with results considered positive when lesion(s) ≥1 cm showed diffusion restriction or mild-moderate T2 hyperintensity. Ultrasonography results were retrieved from patient records. HCC was diagnosed histologically and/or radiologically. Sensitivity, positive predictive value (PPV), specificity, and negative predictive value (NPV) were evaluated using generalized estimating equations.

Results: Forty-eight HCCs were diagnosed in 43 patients. Per-lesion and per-exam sensitivities of non-enhanced MRI were 77.1% and 79.1%, respectively, which were higher than those achieved with ultrasonography (25.0% and 27.9%, respectively, p <0.001). Specificities of non-enhanced MRI (97.9%) and ultrasonography (94.5%) differed significantly (p <0.001). NPV was higher for non-enhanced MRI (99.1%) than ultrasonography (96.9%). Per-lesion and per-exam PPVs were higher for non-enhanced MRI (56.9% and 61.8%, respectively) than for ultrasonography (16.7% and 17.7%, respectively). The estimated scan time of non-enhanced MRI was <6 min.

Conclusion: Based on its good performance, short scan times, and the lack of contrast agent-associated risks, non-enhanced MRI is a promising option for HCC surveillance in high-risk patients.

Lay summary: Recently revised international guidelines for hepatocellular carcinoma (HCC) suggest that selected patients with inadequate surveillance on ultrasonography be assessed by alternative imaging modalities such as computed tomography or magnetic resonance imaging (MRI). Herein, we show that MRI without contrast agents performed significantly better than ultrasonography for HCC surveillance in high-risk patients. Given this good performance, as well as short scan times and the lack of contrast agent-associated risks, non-enhanced MRI is a promising option for HCC surveillance in high-risk patients.

Keywords: CT; Contrast agents; HCC; MRI; Surveillance; Ultrasound.