Multidetector CT of Extrahepatic Bile Duct Cancer: Diagnostic Performance of Tumor Resectability and Interreader Agreement.

Background In extrahepatic bile duct (EHD) cancer, accurate assessment of resectability is essential for curative surgery, but pertinent guidelines from the perspectives of radiologists are yet to be developed. Purpose To investigate the performance of multiphasic CT in the assessment of longitudinal tumor extent, vascular invasion, and resectability of EHD cancer according to the Korean Society of Abdominal Radiology consensus recommendation and to evaluate the interreader agreement. Materials and Methods This retrospective study included patients with EHD cancer who underwent multiphasic CT examinations with section thickness of 3 mm or less before surgery from January 2016 to December 2018. Four abdominal radiologists independently evaluated the overall and biliary segment-wise longitudinal tumor extent, the presence of hepatic artery and/or portal vein invasion, and the resectability according to the Korean Society of Abdominal Radiology recommendations. The diagnostic performance was assessed with sensitivity, specificity, accuracy, and area under the receiver operating characteristic curve. Interreader agreement was determined using κ statistics. Results A total of 112 patients (mean age ± SD, 61 years ± 11; 73 men) were evaluated. The accuracy of the overall longitudinal tumor extent assessment ranged from 56.3% (63 of 112 patients) to 74.1% (83 of 112 patients). The sensitivity for detecting secondary confluence involvement (n = 62) was lower than that for the primary confluence or intrapancreatic duct (n = 115; 38.5%-75% vs 72.1%-96.3%, respectively). Vascular invasion (n = 17) had moderate sensitivity (28.6%-71.4%) and high specificity (77.5%-99.0%). For predicting negative-margin (R0) resection (n = 85), the sensitivity and specificity ranged from 71.8% to 96.5% and from 11.1% to 66.7%, respectively, and the areas under the receiver operating characteristic curve ranged from 0.69 to 0.80. Interreader agreements for tumor extent, vascular invasion, and resectability had κ values of 0.65-0.89, 0.21-0.64, and 0.35-0.56, respectively. Conclusion For the preoperative evaluation of extrahepatic bile duct cancer, the Korean Society of Abdominal Radiology consensus recommendation enabled systematic assessment of longitudinal tumor extent and vascular invasion with acceptable performance in predicting negative-margin resection with use of multiphasic CT and with fair to good interreader agreement. © RSNA, 2022 Online supplemental material is available for this article.