CEACAM5 and gastric cancer: The expression level of hsa_circ_0001811 in gastric cancer tissue correlated with carcinoembryonic antigen (CEA) (P = .0347), tissue differentiation (P = .0138), and lymph node metastasis (P = .0234), while plasma hsa_circ_0001811 level was related to carbohydrate antigen (CA19‐9) (P = .0278), lymph node metastasis (P = .0469), distant metastasis (P = .0384), and age (P = .0085).