Prognostic impact of the metastatic lymph node number in intrahepatic cholangiocarcinoma

Background: Lymph node metastasis in intrahepatic cholangiocarcinoma is a poor prognostic factor after radical surgery. However, unlike other biliary tract malignancies, the nodal stage of intrahepatic cholangiocarcinoma only reflects the presence of metastatic lymph nodes, not the number of metastatic lymph nodes. This study aimed to identify the prognostic impact of the metastatic lymph node number in intrahepatic cholangiocarcinoma. Methods: The data from 87 patients with intrahepatic cholangiocarcinoma who had undergone hepatectomy with 5 or more harvested lymph nodes and covering stations 12 and 8 based on the previous criteria from January 2006 to December 2019 were retrospectively reviewed. The hazard ratio according to the increasing metastatic lymph node number was calculated with other known prognostic factors for intrahepatic cholangiocarcinoma. The patients were then divided into 3 groups according to the metastatic lymph node number (N0 [n = 45]: no metastatic lymph nodes; N+ <4 [n = 32]: 1 to 3 metastatic lymph nodes; N+ ≥4 [n = 10]: ≥4 metastatic lymph nodes). Disease-free survival and overall survival were also analyzed. Results: The metastatic lymph node number was a prognostic factor of oncologic survival (disease-free survival: hazard ratio = 1.18 [1.05-1.32], P = .005; overall survival: hazard ratio = 1.21 [1.06-1.37], P = .004). Survival analysis revealed significantly poorer outcomes with an increasing metastatic lymph node number (disease-free survival: N0 vs N+ <4 vs N+ ≥4: 36.0 [0.0-76.0] vs 8.0 [0.0-16.9] vs 2.0 [0.0-5.1] months, P < .001; overall survival: N0 vs N+ <4 vs N+ ≥4: 69.0 [24.5-113.5] vs 28.0 [18.9-37.1] vs 11.0 [6.4-15.6] months, P < .001). In post hoc analysis, a significant difference was found between adjacent groups (disease-free survival and overall survival: N+