Diagnostic usefulness of KL-6 concentration of bile in biliary tract cancer

The sensitivity of bile cytology for biliary tract cancer varies from 6-64%, and hence remains unsatisfactory. Sialylated carbohydrate antigen KL-6 mucin is positive in biliary tract cancer tissues and serum KL-6 levels are significantly increased in intrahepatic ductal adenocarcinoma patients compared with healthy individuals. The aim of the present study was to evaluate the usefulness of the KL-6 concentration of bile for the diagnosis of biliary tract cancer. Bile cytology and measurements of bile KL-6 concentration were conducted for 43 patients (25 biliary tract cancers and 18 benign biliary disease). The concentration of KL-6 in the bile of the biliary tract cancer group was compared with the benign biliary disease group. The diagnostic ability was assessed by using receiver operating characteristic curves (ROC). The mean KL-6 concentration of bile for biliary tract cancer (34.6±51.6 U/ml) was increased compared with benign biliary disease (5.2±3.9 U/ml, P<0.001). The area under the ROC for diagnosis of biliary tract cancer was 0.84 for benign biliary disease. When the cut-off level of the KL-6 concentration of bile was 8.6 U/ml, the sensitivity, specificity, and accuracy of the KL-6 concentration of bile alone for the diagnosis of biliary tract cancer were 72, 89, and 79%, respectively. Adding the bile KL-6 concentration to bile cytology measurements, the sensitivity for the diagnosis of biliary tract cancer was increased significantly (100%, P=0.0184). The KL-6 concentration of bile may strengthen the sensitivity of bile cytology for biliary tract cancer.