Background: 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.
Methods: 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.
Results: 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).
Conclusions: 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.
Keywords: Examined lymph nodes; Intrahepatic cholangiocarcinoma; Nodal staging score model; Staging; Surgical resection.
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