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.