Introduction : Lymph node (LN) metastasis in intrahepatic cholangiocarcinoma (ICC) is one of the poor prognostic factors after radical surgery. However, unlike other biliary tract malignancies, the nodal stage of ICC only reflects the presence of metastatic LN, not the number of metastatic LNs. This study aims to identify the prognostic impact of metastatic LN numbers in ICC.

Methods : Data from 97 ICC patients who underwent radical hepatectomy (R0) with 6 or more LNs harvested from January 2000 to December 2018 were retrospectively reviewed. The patients were divided into 3 groups according to the number of metastatic LNs. (N0 group (n=52): no metastatic LN, N1 group (n=33): 1-3 metastatic LNs, N2 group (n=12): ≥4 metastatic LNs) Disease-free survival (DFS) and overall survival (OS) were analyzed using the log rank test.

Results : In DFS analysis, significantly poor outcomes were shown with an increasing number of metastatic LNs. (N0: 33.0 months [12.1-53.9], N1: 9.0 months [0.0-18.0], N2: 6.0 months [4.9-7.1], p<0.001) In the post hoc analysis, a significant difference between adjacent groups was shown. (N0 vs. N1: p=0.006, N1 vs. N2: p=0.011) In OS analysis, significantly poor outcomes were shown with an increasing number of metastatic LNs as well. (N0: 84.0 months [45.4-122.6], N1: 36.0 months [17.6-54.4], N2: 25.0 months [8.9-41.1], p<0.001) In the post hoc analysis, a significant difference between adjacent groups was also shown. (N0 vs. N1: p=0.031, N1 vs. N2: p=0.017)

Conclusions : With proper LN dissection, the number of metastatic LNs is a prognostic factor of ICC.