Impact of Lymph Nodes Examined on Survival in ypN0 Gastric Cancer Patients: a Population-Based Study

Background Our aim was to evaluate the prognostic value of the number of lymph nodes examined (eLNs) on survival in ypN0 gastric cancer (GC) patients, and further to define the optimal number of lymph nodes needed to be examined during radical gastrectomy of ypN0 GC patients. Methods A total of 1127 ypN0 GC patients during 2004–2015 from the Surveillance, Epidemiology, and End Results (SEER) database were included. The number of eLNs cutoff points that determined the greatest actuarial survival difference was calculated by the X-tile program. Univariate and multivariate analyses were performed to assess the impact of eLNs on overall survival (OS). Results The optimal number of eLNs thresholds was determined to be 15 for ypN0 GC patients. Kaplan-Meier analysis revealed that ypN0 GC patients with ≥ 16 eLNs had a significantly better OS than those with ≤ 15 eLNs (5-year OS; 60.8 vs 45.4%, P < 0.001). Similarly, multivariate Cox analysis revealed that ypN0 GC patients with ≥ 16 eLNs experienced a significantly lower hazard of death than those with ≤ 15 eLNs (adjusted HR; 0.73, 95% CI, 0.60–0.90, P = 0.003). Conclusions The number of eLNs was an independent predictor of survival for ypN0 GC patients. A minimum of 15 eLNs is recommended as the cutoff point for the evaluation of the quality of postoperative or prognostic stratification in ypN0 GC patients.