Kim DH et al. (2007) CT colonography versus colonoscopy for the detection of advanced neoplasia. N Engl J Med 357: 1403–1412

Many colorectal carcinomas are prevented by the detection and removal of advanced adenomas that are ≥10 mm in diameter, have a substantial villous component and show high-grade dysplasia (classed as advanced adenomas). Polypectomy is recommended if advanced neoplastic lesions are found. The standard method for colorectal screening is optical colonoscopy (OC), which combines endoscopy with the excision of adenomas.

Although generally successful, OC is also invasive. Since only a small proportion of all adenomas are advanced, a reliable noninvasive detection method, such as CT colonography (CTC), to enable selective polypectomy could be advantageous. Kim et al. compared OC and CTC in patients attending routine colorectal screening programs in one institution.

Primary CTC screening in 3,120 consecutive adults detected 123 advanced neoplasms, including 14 invasive cancers. Primary OC screening in 3,163 consecutive adults detected 121 advanced neoplasms, including 4 invasive cancers. Advanced neoplasia was confirmed in 100 (3.2%) patients in the CTC group and 107 (3.4%) patients in the OC group.

In the OC group, polyps were removed during primary OC irrespective of size. Hence, 2,434 polypectomies were performed, resulting in seven colonic perforations. Referral for OC was offered to the 7.9% of patients in the CTC screening group who had polyps ≥6 mm in size, resulting in 561 polypectomies, with no colonic perforations. The authors suggest that primary CTC with selective OC can achieve similar results to OC screening but with much lower polypectomy rates.