Novel staging system using carbohydrate antigen (CA) 19-9 in extra-hepatic cholangiocarcinoma and its implications on overall survival

Abstract Background CA19-9 elevation has shown to be associated with poor prognosis in extrahepatic cholangiocarcinoma (ECCA). However, the role of CA19-9 in staging of ECCA has not been evaluated. We hypothesized that CA19-9 elevation is a marker of aggressive biology in ECCA and that inclusion of CA19-9 in the staging system may improve overall survival (OS) discrimination. Methods Patients with ECCA whose CA19-9 levels, irrespective of surgical status, were reported to the National Cancer Database (2004–2015) were included. The patients were classified based on their CA19-9 levels and a new staging system was proposed. Net reclassification improvement (NRI) model was used to assess the predictive improvement in the proposed survival model as compared to AJCC-TNM staging. Results Of the 2100 patients included in the study, 626 (32%) and 1474 (68%) had normal and elevated CA19-9 levels (>38 U/ml), respectively. Median OS was lower among patients with elevated CA19-9 level compared to those with CA19-9 level ≤38 U/ml (8.5 vs 16 months, p  Conclusion Elevated CA19-9 was found to be an independent risk factor for mortality in ECCA and its inclusion in the proposed staging system improved OS discrimination.