The high expression level of CST2, CST4, CST5, and CST6 in patients with GC was significantly correlated with poor prognosis (P = 0.018, HR = 1.48, 95% CI = 1.07–2.06; P = 0.018, HR = 1.48, 95% CI = 1.07–2.06; P = 0.010, HR = 1.53, 95% CI = 1.10–2.13; P = 0.030, HR = 1.43, 95% CI = 1.03–1.99, respectively). This evidence concerns the gene CST5 and gastric cancer.