BackgroundIn clinical practice, carcinoembryonic antigen (CEA) and carbohydrate antigen (CA) 19-9 are the most common markers measured before and after surgery for gastric cancer (GC). However, which pre- or post-operative combined tumour markers (CEA and CA19-9) have more prognostic value remains unclear.MethodsConsecutive patients undergoing a resection for GC at the Fujian Medical University Union Hospital were included as a discovery database between January 2011 and December 2014. The prognostic impact of pre- and post-operative tumour markers was evaluated using Kaplan–Meier log-rank survival analysis and multivariable Cox regression analysis. The results were then externally validated.ResultsA total of 735 and 400 patients were identified in the discovery cohort and in the validation cohort, respectively. Overall survival rates decreased in a stepwise manner in association with the number of pre- and post-operative positive tumour markers (both P < 0.001). Multivariable analysis revealed that the number of pre-operative positive tumour markers was an independent prognostic factor (P < 0.05). For patients with abnormal pre-operative tumour markers, normalisation of tumour markers after surgery is an independent prognostic protective factor (hazard ratio (HR) = 0.618; 95% confidence interval (CI) = 0.414–0.921), and patients with both positive post-operative tumour markers had double the risk of overall death (HR = 2.338; 95% CI = 1.071–5.101). Similar results were observed in the internal validation and external validation cohorts.ConclusionPre-operative tumour markers have a better discriminatory ability for post-operative survival in GC patients than post-operative tumour markers, and the normalisation of tumour markers after surgery was associated with better survival.