Proposal of the optimal numbers of examined and positive lymph nodes to the 8th edition of American Joint Committee on Cancer (AJCC) staging for 758 patients with distal cholangiocarcinoma.

Introduction: The American Joint Committee on Cancer (AJCC) recommended retrieval of at least 12 lymph nodes and firstly classified N category by the number of positive lymph nodes (PLNs) for Distal Cholangiocarcinoma (DCC).

Objective: The end of this cohort study was to explore the optimal cut-off values of the number of examined lymph nodes (ELNs) and PLNs to better stratify patients by utilizing a population-based database.

Methods: A number of 758 patients with DCC from the Surveillance, Epidemiology, and End Results (SEER) database were enrolled in the study and comparing by the survival analysis.

Results: Survival analysis found that patients with ELNs < 5 had a lower 3-year disease-specific survival rate than ELNs ≥ 5 in N0M0 cohort (35.3% vs. 53.0%, P = 0.001) and in M0 cohort (42.7% vs. 32.8%, P = 0.006); survival curves between patients with ELNs < 12 and ELNs ≥ 12 were overlapped in N0M0 cohort (P = 0.256) and in M0 cohort (P = 0.233). Among patients with ELNs ≥ 5, using the optimal cut-off value of the number of PLNs (0, 2) could accurately stratify patients, but the recommendation of the number of PLNs (0, 3) by the AJCC could not.

Conclusions: This study recommended examining at least 5 lymph nodes and defining PLNs = 1-2 as the N1 category and PLNs ≥ 3 as the N2 category, which may better stratify distal cholangiocarcinoma patients and improve the accuracy of the eighth edition AJCC staging.