A multicenter prospective adapttive trial (Non-comparative phase2 and non-inferiority phase3 study) of underwater endoscopic miucosal resection (UEMR) compared to endoscopic submucosal dissection (ESD) for early colorectal cancer.

Interventions: ESD or UEMR Primary outcome(s): Pathological complete resection rate [The tumor component in the resected specimen shall be negative for horizontal margin and negative for vertical margin (R0 resection).] Study Design: randomized controlled trial, open(masking not used), active control, parallel assignment, treatment purpose