No prophylactic defect closure

The goal of this clinical trial is to compare adverse even rates after EMR for large (≥20mm) flat colorectal polyps (so-called laterally spreading lesions, LSLs) when performing complete or no defect closure. It will also evaluate lesion recurrence after EMR for large colorectal LSLs. The hypothesis is that performing complete defect closure following EMR of large colorectal LSLs will result in lower rates of adverse events compared to cases where no defect closure is performed. For participants with planned EMR, endoscopists will perform EMRs as per standard of care and: * prophylactic defect closure will either not be performed (control group), or will be performed (experimental group); * then, patients will be called between 14 and 44 days after EMR to assess for possible adverse events, and electronic medical files will be verified for emergency room visits and healthcare received for an adverse event; * finally, patients will undergo follow-up colonoscopy 6 months and 18 months after randomization.