Endoscopic Submucosal Dissection (ESD) Versus Endoscopic Mucosal Resection (EMR) for Large Non Pedunculated Colonic Adenomas: a Randomized Comparative Trial

Inclusion Criteria: * Patient suffering from non-pedunculated polyp suspected larger than 25 mm in the colon * Colon localization beyond 15 cm of the anal margin. * Indication for endoscopic treatment * Patients aged ≥ 18 years old * Patients able to fill in questionnaires written in French Exclusion Criteria: * Prior endoscopic resection attempt * Contra-indication to colonoscopy * Contra-indication to general anesthesia * Inability to stop antiplatelet agents and anti-coagulant according to the European Society of Gastro-Intestinal Endoscopy guidelines. * Recurrent adenoma: post-endoscopic or surgical resection * Pregnant or lactating women * Genetic polyposis (Familial Adenomatous Polyposis, Lynch Syndrome, Peutz-Jeghers Syndrome) * Inability to provide informed consent * Patient under legal protection and or deprived of liberty by judicial or administrative decision * Patient already participating in an interventional clinical research protocol * Patient who cannot be followed for the duration of the study * Non-pedunculated polyp ≤ 25 mm * More than one lesion \> 25 mm that fulfilled the inclusion criteria * Suspicion of deep submucosal cancer by analysis of macroscopic appearance (Paris 0-III), vascular pattern and pit pattern (SANO IIIB, KUDO Vn) * Non granular pseudodepressed Laterally spreading tumors due to the high risk of nonvisible submucosal cancer * Polyp involving the appendice deeply (type 2 or 3 of classification of Toyonaga) * Polyp inside the ileo-caecal valvula * Tattoing under the lesion * Inflammatory Bowel Disease with expected fibrosis (Crohn disease or ulcerative colitis) * Colon localization \< 15 cm of the anal margin. * Polyp invading a diverticulum * Pedunculated polyp * Absence of lesion