Patients with polyps larger than 5 mm in computed tomography colonoscopy screening have high risk for advanced colonic neoplasia in Asia

Background & aims: Computed tomography colonography (CTC) is a recommended screening modality for colorectal cancer (CRC). It is not known whether polyps 6-9 mm based on CRC are likely to have advanced histologic features in Asian patients. We estimated the risk of advanced colonic neoplasia (ACN) from polyps <10 mm and the risk of ACN detection failure if patients with polyps <10 mm are not referred for colonoscopy.

Methods: The study included 1457 subjects from the Asia-Pacific Working Group on CRC screening and the Hong Kong CRC screening program. Polyps and ACN found during colonoscopy examinations were classified by size and histology.

Results: Of the subjects, 38.2% had polyps; 16.7% of these were ACN, 5.4% of ACN were ≤5 mm, and 24.7% of the ACN were 6-9 mm. Adopting the policy of reporting polyps found by CTC of <5 mm as normal and repeating CTC in patients with polyps of 6-9 mm, 5.4% of subjects with ACN, 4.5% of male subjects, and 11.5% of subjects with family history of CRC would be classified as normal. In referring patients with polyps of 6-9 mm for CTC surveillance, 20.4% of those with ACN, 22.4% of those that are male, and 23.1% of those with family histories of CRC would have polypectomies delayed by at least 3 years.

Conclusions: A substantial proportion of polyps <10 mm have advanced histologic features in Asia, so patients with a polyp of 6 mm or more at CTC should be offered colonoscopies with polypectomies, rather than CTC surveillance of polyps.