The optimal number of examined lymph nodes for accurate staging of intrahepatic cholangiocarcinoma: A multi-institutional analysis using the nodal staging score model

This study aims to develop a nodal staging score (NSS) to determine the optimal number of lymph nodes (LNs) examined in intrahepatic cholangiocarcinoma (iCCA) patients.Clinicopathologic data were collected from the SEER database (development cohort, n = 2782) and seven Chinese tertiary hospitals (validation cohort, n = 363). NSS was constructed based on a binomial distribution to indicate the probability of nodal disease absence. In addition, its prognostic value was examined by survival analysis and multivariable modeling on pN0 patients.A model fit was performed in node-positive patients and a subgroup analysis was performed according to clinical characteristics. Statistically significant differences were only found in the subgroups when divided by the tumor size of 3 cm. As the number of examined lymph nodes (ELNs) increased, the likelihood of missing a metastatic LN decreased. NSS escalated as ELNs increased in groups with different tumor sizes, with plateaus at 7 and 11 LNs ensuring an NSS of 90.0% for ≤3 cm and >3 cm tumors, respectively. For pN0 patients, multivariate analysis revealed that NSS was an independent prognostic factor for overall survival (OS) and recurrence-free survival (RFS).For accurate staging of iCCA, the optimal number of ELNs was related to tumor size. We recommend that at least 7 and 11 LNs should be examined for tumor size ≤3 cm and >3 cm, respectively. Therefore, the NSS model could be helpful to make clinical decisions for pN0 iCCA.