CS-iCCA, A New Clinically Based Staging System for Intrahepatic Cholangiocarcinoma: Establishment and External Validation

INTRODUCTION: Intrahepatic cholangiocarcinoma (iCCA) is a primary liver malignancy with poor prognosis. Current prognostic methods are most accurate for patients with surgically resectable disease. However, a significant proportion of patients with iCCA are not surgical candidates. We aimed to develop a generalizable staging system based on clinical variables to determine prognosis of all patients with iCCA. METHODS: The derivation cohort included 436 patients with iCCA seen between 2000 and 2011. For external validation, 249 patients with iCCA seen from 2000 to 2014 were enrolled. Survival analysis was performed to identify prognostic predictors. All-cause mortality was the primary end point. RESULTS: Eastern Cooperative Oncology Group status, tumor number, tumor size, metastasis, albumin, and carbohydrate antigen 19-9 were incorporated into a 4-stage algorithm. Kaplan-Meier estimates for 1-year survival were 87.1% (95% confidence interval [CI] 76.1–99.7), 72.7% (95% CI 63.4–83.4), 48.0% (95% CI 41.2–56.0), and 16% (95% CI 11–23.5), respectively, for stages I, II, III, and IV. Univariate analysis yielded significant differences in risk of death for stages II (hazard ratio [HR] 1.71; 95% CI 1.0–2.8), III (HR 3.32; 95% CI 2.07–5.31), and IV (HR 7.44; 95% CI 4.61–12.01) compared with stage I (reference). Concordance indices showed the new staging system was superior to the TNM staging for predicting mortality in the derivation cohort, P < 0.0001. In the validation cohort, however, the difference between the 2 staging systems was not significant. DISCUSSION: The proposed independently validated staging system uses nonhistopathologic data to successfully stratify patients into 4 stages. This staging system has better prognostic accuracy compared with the TNM staging and can assist physicians and patients in treatment of iCCA.