Aspirin and/or clopidogrel users are increasing due to increased prevalence of cardiovascular or cerebrovascular disease with an aging society in Korea. Also, the patients having endoscopic mucosal resection (EMR) or endoscopic submucosal dissection (ESD) for early gastric cancer or gastric premalignant lesions including adenoma and dysplasia are increasing among aspirin and/or clopidogrel users. Practically, aspirin or clopidogrel is recommended to be stopped for 5~14 days before EMR or ESD because bleeding risk during or after procedure. And it is recommended to restart of aspirin and/or clopidogrel as soon as possible if immediate bleeding during or after the procedure is not occurred in consideration of thromboembolic risk. However, early restarting of aspirin and/or clopidogrel raise the risk of delayed bleeding and the risk of complications associated with delayed ulcer healing. Although it is important to determine the timing of restarting aspirin and/or clopidogrel in consideration of complications of post-EMR/ESD ulcer and thromboembolic risk, there is no definite guideline about the timing of restarting aspirin and/or clopidogrel.

This study is aimed to determine the timing of restarting aspirin and/or clopidogrel for the patients having EMR or ESD among aspirin and/or clopidogrel users. The investigators planned to compare the delayed bleeding rate and ulcer healing rate in patients with post-EMR/ESD ulcer when take proton pump inhibitor (pantoprazole 40 mg per day) between the patients restarting aspirin and/or clopidogrel within 3~4 days after the procedure and the patients restarting aspirin and/or clopidogrel 2 weeks after the procedure during 4 weeks. The primary endpoint is delayed ulcer bleeding rate at 4 weeks after EMR/ESD. The secondary end point is ulcer healing rate within 4 weeks.

Inclusion Criteria:

• Patients who have taken aspirin and/or clopidogrel for cardiovascular and/or cerebrovascular disease and are found to have early gastric cancer or premalignant lesions including adenoma and dysplasia by upper endoscopy.

Exclusion Criteria:

• Patients with known coagulopathy or abnormal coagulation tests (prothrombin time, partial thromboplastin time and platelet count)
• Patients receiving other antithrombotic, anticoagulant drugs
• Patients needing continuation of nonsteroidal anti-inflammatory drugs, cyclooxygenase-2 (COX-2) inhibitors, or steroid after EMR/ESD
• Patient with recent percutaneous coronary intervention (placement of drug eluting coronary artery stent within 12 months, bare metal coronary artery stents within 1 month)
• Patient's age > 80 year-old or < 18 year-old
• Patient with severe cardiovascular, pulmonary, hepatic, or renal disease