The Evaluation of the Eighth Edition of the AJCC/UICC Staging System for Intrahepatic Cholangiocarcinoma: a Proposal of a Modified New Staging System

Background The objective was to clarify the prognostic impact of the 8th edition of American Joint Committee on Cancer (AJCC)/International Union Against Cancer (UICC) of intrahepatic cholangiocarcinoma (ICC). Methods A total of 103 ICC patients who underwent hepatectomy between 2002 and 2016 were enrolled. The survival impact of AJCC/UICC 8th edition was examined. Results The 5-year disease-specific survival (DSS) rate was 75.9% in T1a (n = 23), 88.9% in T1b (n = 10), 14.9% in T2 (n = 24), 52.5% in T3 (n = 11), and 15.2% in T4 (n = 35). The DSS was comparable among T2, T3, and T4 (T2 vs. T3; p = 0.345, T3 vs. T4; 0.295). A multivariate analysis identified multiple tumors (hazard ratio [HR] 2.821), periductal infiltrating (HR 2.439), perforation of the visceral peritoneum (HR 1.850), and vascular invasion (HR 1.872) as independent prognostic factors that were associated with the DSS. The optimum tumor size with the greatest difference in the DSS was 2 cm (p = 0.014). The new T classification was developed as follows: T1, size <= 2 cm without other factors; T2, size > 2 cm without other factors; T3, vascular invasion or perforation of the visceral peritoneum; and T4, multiple tumors or periductal infiltrating. The 5-year DSS was 100% in T1 (n = 7), 76.6% in T2 (n = 28), 45.1% in T3 (n = 28), and 3.4% in T4 (n = 40). There were differences in the DSS between T2 and T3 (p = 0.035) and between T3 and T4 (p = 0.003). Conclusions T2, T3, and T4 of AJCC/UICC overlapped with regard to the DSS. The new staging can classify ICC patients with sufficient prognostic differences.