Study on gastric cancer diagnosis by endoscopy

INTERVENTION: arm A:First observation:WLI + Second observation:NBI arm B:First observation:NBI + Second observation:WLI CONDITION: gastric cancer PRIMARY OUTCOME: Proportion of patients with gastric cancer and/or adenoma detected by non‐magnifying endoscopy of the first observation SECONDARY OUTCOME: 1) Proportion of patients with overlooked gastric cancer and/or adenoma (detected by non‐magnifying endoscopy of the second observation); 2) Proportion of patients with gastric cancer detected by non‐magnifying endoscopy of the first observation ; 3) Positive predictive value (PPV) for diagnosis of gastric cancer and/or adenoma in non‐magnifying endoscopy of the first observation; 4) Sensitivity and specificity of gastric cancer diagnosis by NBI with magnifying endoscoy; 5) Proportion of adverse events; 6) Observation time INCLUSION CRITERIA: 1) The age to obtain consent is 18 or older 2) Fulfill any of the following [1]‐[3]. [1] Patients who have previously undergone endoscopic treatment for early gastric cancer or gastric adenoma and are currently being monitored at our site. [2] Patients who have not received treatment for early gastric cancer or gastric adenoma and are currently being monitored at their own site. [3] Patients who are scheduled to undergo an endoscopy for the purpose of detailed examination of gastric cancer or gastric adenoma. 3) It has been at least si Xmonths since the patient underwent endoscopy at your site. 4) Written informed consent has been obtained for participation in the study.