Nomogram with insufficient examined lymph node count to help T3N0M0 gastric cancer patients with adjuvant chemotherapy selection–a population-based study combined with external validation

Abstract Objective Whether chemotherapy is required for T3N0M0 gastric cancer patients after surgery is controversial. Methods Using the National Cancer Institute Surveillance, Epidemiology, and End Results (SEER) database, 420 patients with pT3N0M0 gastric cancer diagnosed after radical resection between 2004 and 2016 were screened for analysis. Survival analysis was performed using the Kaplan-Meier method and the log-rank test. Cox proportional hazards regression analysis was used to screen independent prognostic factors and build a nomogram survival prediction model. The patients were divided into three groups of low, moderate, and high risk using X-tile software according to the risk score. A total of 335 patients with pT3N0M0 gastric cancer diagnosed between 2000 and 2013 at our hospital were used for external validation. Results Multivariate analysis revealed that age, histology, and examined lymph node count were independent prognostic factors for pT3N0M0 gastric cancer in the group without adjuvant therapy and were therefore included in the nomogram prediction model. The concordance index for the nomogram model was 0.628 (95% confidence interval, 0.542–0.714). All patients were divided into three risk subgroups according to the nomogram prediction score. The analysis results showed that adjuvant chemotherapy did not improve the prognosis of low risk patients, while moderate and high risk patients benefited from it. External validation was consistent with the SEER database results. Conclusion The model demonstrated that only moderate and high risk patients were recommended to receive adjuvant chemotherapy, while low risk patients were not.