In the meta-analysis, the prognostic effects of pretreatment serum CEA on OS (HR 1.716, 95% CI 1.594–1.848), DSS (HR 1.940, 95% CI 1.563–2.408) and DFS (HR 2.275, 95% CI 1.836–2.818) in patients with gastric cancer were confirmed (Fig 2). This evidence concerns the gene CEACAM5 and gastric cancer.