Movement of a novel serum tumour marker, RCAS1, in patients with biliary diseases

Background. We have demonstrated immunohistochemically that RCAS1 antigen is expressed in biliary neoplasms. Serum RCAS1 levels are also elevated in a high percentage of patients with intra-hepatic cholangiocarcinoma. Aim. The study was designed to determine whether serum levels of RCAS1 are of clinical significance as a tumour marker for biliary tract tumour, in comparison to CA19-9. Patients and methods. In 38 patients with biliary carcinoma (gallbladder carcinoma, extra-hepatic and intra-hepatic cholangiocarcinoma and ampullary carcinoma), we measured serum RCAS1 and CA19-9 levels. For control, serum samples from patients with benign biliary disease and healthy volunteers were also examined. Results. We established a threshold value for RCAS1 of 17.5 U/ml, which permitted discrimination between malignant and non-malignant biliary diseases. In comparison to CA19-9, serum RCAS1 was more sensitive and specific for malignancy, and was not influenced by cholestasis. RCAS1 levels varied with respect to the disease course and the effect of clinical treatment. Conclusions. Serum RCAS1 appears to be valuable as a diagnostic index for biliary carcinomas, as well as for evaluating the progression of cancers during therapy. We speculate that RCAS1 is a clinically more significant serum marker for biliary neoplasms than CA19-9.