The investigators have recently become proficient in a new, and we believe more effective technique for polyp removal. Known as Endoscopic Submucosal Dissection (ESD). ESD involves removing the polyp in one piece. It is preferable to remove the polyp in one piece as it minimises the chance of leaving residual polyp tissue behind. There have also been recent studies overseas that have shown this new technique to be quite effective. In this study, half of the patients will receive the newly developed technique of polyp removal (ESD), while the other half will receive conventional Endoscopic Mucosal Resection (EMR) treatment. This study will allow us to show which technique results in lower recurrence rates and is more effective.

EMR is a very effective procedure for lesions smaller than 20 mm. With this size the polyp can be removed en bloc. En bloc resection is preferred as it minimises the likelihood of residual adenoma and enhances histological assessment. It is also curative in superficially invasive submucosal disease. It eliminates the need for surgery in these patients. With lesions larger than 20 mm, the lesion is removed piece meal, often in more than 5 pieces. Care is taken to ensure that no adenoma is left behind at the point of overlap between snare resections. However, for every additional snare resection, there is the possibility that a small amount of adenoma will be left behind at this overlap point. Overall, the literature suggests that there is approximately a 15% residual adenoma rate at repeat colonoscopy in 3 months, which requires further treatment. With en bloc resection residual adenoma rate at repeat colonoscopy in is close to 0%. This has to be balanced against the relative inexperience with performing ESD, longer procedure time and higher complication rates. A randomized trial near completion is comparing endoscopic snare resection with transanal surgical resection for rectal polyps (24). Should this trial show that en bloc resection is superior in achieving complete resection without recurrence at similar complication rates, the endoscopic treatment strategy of large colorectal adenomas should be reconsidered. Since en bloc resection is technically more challenging, this should have consequences for credentialing, referral patterns and performance of removal of large colorectal polyps in reference centers only. Thus, before en bloc resection is promoted as superior, and training has to be intensified to comply with standards of safe oncologic resection of these lesions, the efficacy and safety have to be proven in a comparative randomized trial.

Inclusion Criteria:

• Can give informed consent to trial participation
• Lesion size 20 mm to 50 mm
• Laterally spreading or sessile polyp morphology

Exclusion Criteria:

• Previous resection or attempted resection of target adenoma lesion
• Endoscopic appearance of invasive malignancy
• Age less than 18 years
• Pregnancy
• Active Inflammatory colonic conditions (e.g. inflammatory bowel disease)
• Use of anticoagulant or antiplatelet agents other than aspirin less than 5 days prior to procedure
• American Society of Anesthesiology (ASA) Grade IV-V