Controlled comparative study for the efficacy between famotidine and omeprazole on prevention of delayed bleeding from ulcer after ESD for early gastric cancer

INTERVENTION: Administration of famotidine 40mg P.O./day for 8weeks Administration of famotidine 40mg P.O./day for 1day and omeprazole 40mg I.V./day for 3days after ESD and omeprazole 20mg P.O./day for 7weeks and 4 days CONDITION: early gastric cancer PRIMARY OUTCOME: Retio of delayed bleeding(hematemesis or melena required endoscopic hemostasis, decreased the hemoglobin count by more than 2g/dl) SECONDARY OUTCOME: The curative rate for ulcer after ESD at 6 weeks later INCLUSION CRITERIA: 1. early gastric cancer patients who undergo ESD 2. patients who are older than 20 years at entry. 3. patients who understand the study contents and give informed consents by themselves