Prospective cohort study to evaluate the effectiveness, safety and long prognosis of endoscopic submucosal dissection for colorectal tumor

INTERVENTION: Eendoscopic submucosal dissection for colorectal tumor CONDITION: colorectal tumor PRIMARY OUTCOME: Prevalence of complete en bloc resection, complication and prognosis in patients with colorectal ESD SECONDARY OUTCOME: Prevalence of local/metastatic recurrence and rate of metachronous colorectal lesion after ESD INCLUSION CRITERIA: 1)Colorectal ESD cases 2)Early colorectal cancer (>20 mm in diameter) for which endoscopic treatment is indicative but for which en bloc resection by snare EMR would be difficult. 3) Adenoma with non‐lifting sign (+) after injection during EMR procedures. 4)Local residual tumor after EMR (>10 mm in diameter) for which en bloc resection by snare EMR would be difficult.