Progression Rates of LR-2 and LR-3 Observations on MRI to Higher LI-RADS Categories in Patients at High Risk of Hepatocellular Carcinoma: A Retrospective Study.

Abstract

<b>BACKGROUND.</b> Reported rates of hepatocellular carcinoma (HCC) for LR-2 and LR-3 observations are generally greater than those expected on the basis of clinical experience, possibly reflecting some studies' requirement for pathologic reference. <b>OBJECTIVE.</b> The purpose of this study was to determine rates of progression to higher LI-RADS categories of LR-2 and LR-3 observations in patients at high risk of HCC. <b>METHODS.</b> This retrospective study included 91 patients (64 men, 27 women; mean age, 62 years) at high risk of HCC who had clinically reported LR-2 (<i>n</i> = 55) or LR-3 (<i>n</i> = 36) observations on MRI who also underwent follow-up CT or MRI at least 12 months after the observation was made. A study coordinator annotated the location of a single LR-2 or LR-3 observation per patient on the basis of the clinical reports. Using LI-RADS version 2018 criteria, two radiologists independently assigned LI-RADS categories on the follow-up examinations. Progression rates from LR-2 or LR-3 to higher categories were determined. A post hoc consensus review was performed of observations that progressed to LR-4 or LR-5. Subgroup analyses were performed with respect to presence of prior HCC (<i>n</i> = 34) or a separate baseline LR-5 observation (<i>n</i> = 12). <b>RESULTS.</b> For LR-2 observations, the rate of progression to LR-4 was 0.0% (95% CI, 0.0-6.7%) and to LR-5 was 3.6% (95% CI, 0.4-13.1%) for both readers. For LR-3 observations, the rate of progression to LR-4 was 22.2% (95% CI, 9.6-43.8%) and to LR-5 was 11.1% (95% CI, 3.0-28.4%) for both readers. Fourteen observations progressed to LR-4 or LR-5 for both readers. Post hoc analysis revealed no instances of progression from LR-2 to LR-4; two, from LR-2 to LR-5; eight, from LR-3 to LR-4; and four, from LR-3 to LR-5. The progression rate from LR-3 to LR-5 was higher (<i>p</i> < .001) among patients with (100.0%) than those without (3.0%) a separate baseline LR-5 observation for both readers. The progression rate from LR-2 to LR-5 was not associated with a separate baseline LR-5 observation for either reader (<i>p</i> = .30). Progression rates were not different (p > .05) between patients with versus those without prior HCC. <b>CONCLUSION.</b> On the basis of progression to LR-4 or LR-5, LR-2 and LR-3 observations had lower progression rates than reported in studies incorporating pathology results in determining progression. <b>CLINICAL IMPACT.</b> The findings refine understanding of the clinical significance of LR-2 and LR-3 observations.