From the Guidelines
Colon cancer screening can be effectively performed using several imaging options, with colonoscopy remaining the gold standard, as recommended by the American College of Physicians in 2019 1. For average-risk individuals starting at age 50, a colonoscopy every 10 years is recommended as it allows direct visualization of the colon and immediate removal of polyps. Some key points to consider when choosing an imaging option for colon cancer screening include:
- CT colonography (virtual colonoscopy) is a good alternative, performed every 5 years, using low-dose radiation to create detailed 3D images of the colon without requiring sedation, though it still requires bowel preparation and cannot remove polyps if found.
- Flexible sigmoidoscopy, performed every 5 years, examines only the lower third of the colon but is less invasive than colonoscopy.
- Double-contrast barium enema is less commonly used now but provides x-ray images of the colon after filling it with barium and air.
- Capsule colonoscopy, involving swallowing a camera-containing capsule, is newer and less widely available but offers a non-invasive option for those who cannot undergo traditional procedures. These imaging methods are crucial for early detection of precancerous polyps and cancer, significantly improving treatment outcomes through early intervention. The choice between methods should be based on individual risk factors, preferences, and medical history, as suggested by the American College of Radiology in 2018 1. Additionally, the NCCN clinical practice guidelines in oncology recommend that colonoscopy is the primary method employed for colorectal cancer screening in average- and high-risk populations, with a 10-year interval between screenings, unless individual risk factors or physician judgment indicate a shorter interval 1.
From the Research
Imaging Options for Colon Cancer Screening
- Computed Tomography (CT) Colonography: CT colonography is a minimally invasive method for CRC screening and diagnosis, which uses low-dose radiation to detect colorectal polyps and cancer 2, 3, 4, 5, 6.
- Magnetic Resonance Colonography (MRC): MRC is another diagnostic approach for colorectal cancer, with a high sensitivity and specificity for detecting colorectal cancer 4.
- Colonoscopy: Colonoscopy is the gold standard for CRC screening, with a high detection rate for advanced colorectal neoplasia (ACN) 2, 5.
- Fecal Immunochemical Test (FIT): FIT is a non-invasive test that detects blood in the stool, with a high sensitivity and specificity for detecting colorectal cancer 2.
Comparison of Imaging Options
- CT Colonography vs. Colonoscopy: CT colonography has a lower detection rate for ACN compared to colonoscopy, but it is a less invasive procedure with a higher participation rate 5.
- CT Colonography vs. MRC: CT colonography has a higher diagnostic value for colorectal cancer compared to MRC, with a higher positive likelihood ratio and area under the receiver operating characteristic curve 4.
Recent Developments and Updates
- CT Colonography: Recent updates on CT colonography include techniques and dose reduction strategies, image display methods, reporting and classification systems, tumor staging capabilities, integration of advanced imaging techniques, and cost-effectiveness and reimbursement 6.
- Reimbursement: CT colonography has been approved for reimbursement by CMS for colorectal cancer screening, which may increase its acceptance and use 3.