SD has become a standard treatment of gastric neoplasm confined to mucosa(epithelium). But after procedure, formation of iatrogenic gastric ulcer is inevitable. And Post ESD ulcer bleeding rate reported about 5% ~ 10% of all cases. Antiplatelet or anti-coagulation treatment might be associated higher incidence of rebleeding after ESD and iatrogenic ulcer bigger than 40mm in size is also associated.

Though several previous study have failed to show efficacy of 2nd look EGD, but those reports pointed out that visible vessels with current bleeding or highly suspect of recent bleeding (Forrest type IA~IIB) was observed about 10~20% of patients. Such patients are at high risk of bleeding.

So, Investigators hypothesize that appliance of Endo-Clot(TM) at post ESD ulcer have a significant role of protection from gastric acidic juice and help mucosa heal earlier. Thus visible vessels with risk of bleeding is going to be rarely observed at 2nd look EGD. And finally this protective effect might have an effect for prophylaxis of post ESD ulcer bleeding.

Inclusion Criteria:

A. Older than 19 years old and younger than 80 years old B. Pathologically confirmed gastric adenoma and/or early gastric cancer C. Iatrogenic gastric ulcer after ESD(Endoscopic submucosal dissection) more than 40mm (at prediction) D. Patients who is taking medication such at aspirin and/or coumadin (and other anti-coagulation medication) E. ECOG performance status 0 or 1 F. Adequate renal function (serum creatinine < 1.5 mg/dL or calculated creatinine clearance ≥ 60 ml/min) G. Adequate liver function (total bilirubin < 1.5 X the upper limits of normal (ULN), AST and ALT <3 X UNL, and alkaline phosphatases < 3 X ULN or < 5 x ULN in case of liver involvement) H. Adequate BM function (WBC ≥ 3,500/µl, absolute neutrophil cell count ≥ 1,500 /µl, platelet count ≥ 100,000/µl) I. Subjects who given written informed consent after being given a full description of the study

Exclusion Criteria:

A. Previously treated by radical gastrectomy B. Adverse effect on this medication C. Pregnant or on breast feeding D. Patients who are unwilling or unable to provide informed consent, such as those with psychiatric problem, drug abuse or alcoholism

Individual participant data will be not shared and used only for this study