Evaluating the adequacy of nodal status in node-negative gallbladder cancer with T1b-T2 stages: use of nodal staging score

Background: The study aimed at establishing a nodal staging score (NSS) to quantify the likelihood that pathologic node-negative gallbladder cancer (GBC) patients are indeed free of lymph node (LN) metastasis.Methods: Clinicopathological data of 1374 GBC patients with T1b-T2 stages were collected from the Surveillance, Epidemiology and End Result database (design cohort [DC], n = 1289) and the First Affil-iated Hospital of Sun Yat-sen University (validation cohort [VC], n = 85). NSS was derived from the count of examined LNs (ELNs) and T stage by using a beta-binomial model, and represented the probability that a node-negative patient is correctly staged. The prognostic value of NSS in node-negative GBC was evaluated by survival analysis.Results: The probability of missing a nodal disease in node-negative GBC patients with T1b-T2 stages (pT1bN0 and pT2N0) decreased as the number of ELNs increased. NSS increased as the number of ELNs increased. For pT1bN0 and pT2N0 patients, examination of 5 and 27 lymph nodes could ensure an NSS of 90.0%, respectively. Multivariate analysis revealed that NSS was an independent predictor for overall survival in pT1bN0 and pT2N0 GBC patients (DC, HR:0.53, 95%CI: 0.42-0.66, p < 0.001; VC, HR: 0.33, 95%CI: 0.14-0.76, p = 0.009).Conclusion: NSS could evaluate the adequacy of nodal staging and predict the prognosis in pT1bN0 and pT2N0 GBC patients, and hence was helpful to guide their treatment strategies.