Development and validation of a nomogram to individually predict survival of young patients with nonmetastatic gastric cancer: A retrospective cohort study

Background/Aims: Evidence regarding gastric cancer (GC) patients <40 years old is limited. The aim of the study was to identify risk factors affecting overall survival (OS) of young patients with nonmetastatic GC and to establish a nomogram for prognostic prediction using data from the Surveillance, Epidemiology and End Results (SEER) database. Furthermore, this study sought to externally validate this nomogram in an independent patient cohort. Patients and Methods: In this retrospective cohort study, the records of patients aged <40 years with nonmetastatic GC (n = 559), from the SEER database, between 2006 and 2015, were examined. The nomogram was established based on the Cox proportional hazards regression model using the SEER dataset. Patients with nonmetastatic GC (n = 201) in our department between 2009 and 2015 were selected as an external validation set. Discrimination and calibration were performed in both cohorts. Results: The multivariate Cox model identified race, tumor subsites, tumor size, depth of invasion, lymph node metastasis, number of examined lymph nodes, and surgery as independent covariates associated with OS. The nomogram exhibited superior discriminative power than the eighth tumor, node, metastasis (TNM) staging system in both the training set [Harrell's concordance index (C index): 0.762 vs. 0.635, P < 0.001] and validation set (C index: 0.805 vs. 0.712, P = 0.176). Calibration of the nomogram was good in both cohorts. Conclusions: We developed a nomogram predicting 3- and 5-year OS rates in young patients with nonmetastatic GC. Both the training set and validation set showed good discrimination and calibration, suggesting good clinical applicability.