Liver Metastases of Intrahepatic Cholangiocarcinoma: Implications for an Updated Staging System.

BACKGROUND AND AIMS: Intrahepatic cholangiocarcinoma (iCCA) with liver metastases is perceived to have a poor prognosis, but the American Joint Committee on Cancer (AJCC) classifies them as early stage in the absence of lymph nodes or extrahepatic spread. APPROACH AND RESULTS: Patients with iCCA from the European Network for the Study of Cholangiocarcinoma (ENS-CCA) and Surveillance, Epidemiology, and End Results (SEER) registries with survival/staging (AJCC v.7) data were eligible. Modified staging was used (mAJCC v.7): group A: stages I-III (excluding T2bN0); group B: stage IVa (excluding T2bN1M0); group C: liver metastases (T2bN0/1); and group D: stage IVb (extrahepatic metastases). Survival analysis (Kaplan-Meier and Cox regression) was performed in an ENS-CCA training cohort (TC) and findings internally (ENS-CCA iVC) and externally (SEER) validated. The aim was to assess whether liver metastases (group C) had a shorter survival compared to other early stages (group A) to propose a modified version of AJCC v.8 (mAJCC v.8). A total of 574 and 4,171 patients from the ENS-CCA and SEER registries were included. Following the new classification, 19.86% and 17.31% of patients from the ENS-CCA and SEER registries were reclassified into group C, respectively. In the ENS-CCA TC, multivariable Cox regression was adjusted for obesity (p = 0.026) and performance status (P < 0.001); patients in group C (HR, 2.53; 95% CI, 1.18-5.42; P = 0.017) had a higher risk of death (vs. group A). Findings were validated in the ENS-CCA iVC (HR, 2.93; 95% CI, 2.04-4.19; P < 0.001) and in the SEER registry (HR, 1.88; 95% CI, 1.68-2.09; P < 0.001). CONCLUSIONS: iCCA with liver metastases has a worse outcome than other early stages of iCCA. Given that AJCC v.8 does not take this into consideration, a modification of AJCC v.8 (mAJCC v.8), including "liver metastases: multiple liver lesions, with or without vascular invasion" as an "M1a stage," is suggested.