The development and external validation of a nomogram predicting overall survival of gastric cancer patients with inadequate lymph nodes based on an international database

Background: Inadequate sampling of lymph nodes could lead to stage migration and indicate a poor prognosis for gastric cancer after curative surgery. Some emerging novel predictors and the application of a nomogram could increase the accuracy of survival prediction. Methods: An international database regarding gastric cancer was employed as the primary cohort. The patients with inadequate (< 30) lymph nodes (LN) were analyzed by Cox proportional hazards regression. Based on the selected model, a nomogram was plotted and calibrated against an external validation database. Results: A total of 1109 patients were included in the primary cohort, and there were 6584 patients in the validation cohort. There were significant differences regarding the clinical characteristics between the two cohorts. The model containing age, T stages, N stages, metastatic lymph nodes (mLN), and the number of total LN retrieved (TLN) showed superiority over the conventional TNM stages. Harrell's concordance index of the nomogram and TNM stages was 0.744 and 0.717, respectively. The external validation demonstrated a good concordance with the nomogram-predicted survival. Conclusions: The nomogram including age, T stages, N stages, mLN, and TLN had a better accuracy than the conventional TNM staging system in predicting overall survival for gastric cancer patients with inadequate (< 30) LN.