Inclusion Criteria:

• Subjects who have advanced colorectal neoplasia* removed and confirmed by histopathology;

• They have received high quality colonoscopies before or during endoscopic resection (defined as a full colonoscopy with successful caecal intubation, and a Boston Bowel Preparation Scale ≧2 in each colonic segment) with no residual colorectal neoplasia;

• Aged 18-90 years old;

• Written informed consent obtained

  • An advanced colorectal neoplasia is defined as an advanced adenoma, sessile serrated lesion or non-invasive colorectal cancer (stage Tis or T1a). Advanced adenoma is defined as an adenoma larger than 10mm, and/or with villous component ≥20%, and/or harboring high grade dysplasia.

Exclusion Criteria:

• Known residual colorectal neoplasia not removed (except hyperplastic polyps);
• Contraindications to endoscopic resection due to deep submucosal invasion (stage T1b or above);
• Prior surgical resection of colon;
• Personal history of hereditary polyposis syndrome or inflammatory bowel disease;
• Known pregnancy or lactation;
• Immunocompromised status (e.g. on immunosuppressants (except 5-aminosalicylic acid or short term use of corticosteroids <4 weeks), on chemotherapy, bone marrow or solid organ transplant, human immunodeficiency virus, congenital immune deficiency);
• Advanced comorbid conditions (defined as American Society of Anesthesiologists grade 4 or above);
• Refusal to undergo surveillance colonoscopy.