The Liver Imaging Reporting and Data System tumor-in-vein category: a systematic review and meta-analysis.

Objectives: We aimed to systematically determine the etiology of the Liver Imaging Reporting and Data System (LI-RADS) tumor-in-vein category (LR-TIV) on contrast-enhanced CT or MRI and to determine the sources of heterogeneity between reported results. Methods: Original studies reporting the etiology of LR-TIV were identified in MEDLINE and EMBASE up until July 7, 2020. The meta-analytic pooled percentages of HCC and non-HCC in LR-TIV were calculated. Subgroup analyses were performed according to the type of reference standard and the most common underlying liver disease. Meta-regression analysis was performed to explore study heterogeneity. Results: Sixteen studies reported the etiology of a total of 150 LR-TIV, of which 98 (65%) were HCC and 52 (35%) were non-HCC. The meta-analytic pooled percentages of HCC and non-HCC in LR-TIV were 70.9% (95% confidence interval [CI], 55.7–82.5%; I² = 59%) and 29.2% (95% CI, 17.5–44.4%; I² = 59%), respectively. The meta-analytic pooled percentage of HCC was lower in studies using only pathology as a reference standard (67.1%; 95% CI, 49.3–81.1%), but higher in studies in which hepatitis C was the most common underlying liver disease (81.9%; 95% CI, 11.3–99.4%) than that in the total 16 studies. Study type (cohort study versus case-control study) was significantly associated with study heterogeneity (p = 0.04). Conclusion: The most common etiology of LR-TIV was HCC. It might be important to understand the percentage of HCC and non-HCC in LR-TIV in consideration of the type of reference standard, geographic differences, and study design. Key Points: • The most common etiology of Liver Imaging Reporting and Data System (LI-RADS) tumor-in-vein category (LR-TIV) was hepatocellular carcinoma (HCC). • The percentage of HCC in LR-TIV was relatively low in studies using only pathology as a reference standard, but high in studies in which hepatitis C was the most common underlying liver disease. • Study type was a factor significantly influencing study heterogeneity. [ABSTRACT FROM AUTHOR]