From the Guidelines
Optical colonoscopy is the preferred screening method for individuals at high risk for colorectal cancer due to family history, as it allows for the detection of dysplasia and the removal of polyps. According to the American College of Radiology Appropriateness Criteria 1, CT colonography is usually appropriate for colorectal cancer screening in individuals at average or moderate risk, but for those at high risk, optical colonoscopy is preferred. The U.S. Multi-Society Task Force on Colorectal Cancer also recommends colonoscopy as the primary screening method for individuals with a high-risk family history, with specific screening intervals and recommendations based on the degree of family history and risk 1. While CT colonography can be an alternative for high-risk patients who cannot undergo colonoscopy, it has limitations, including the inability to remove polyps and potential radiation exposure.
Some key points to consider when evaluating screening options for high-risk patients include:
- The ability to detect and remove polyps, which is a key advantage of optical colonoscopy
- The risk of radiation exposure associated with CT colonography
- The importance of individualized screening recommendations based on family history and risk factors
- The need for patients to discuss their screening options with their healthcare provider and determine the best approach based on their individual needs and circumstances.
In terms of specific screening recommendations, the U.S. Multi-Society Task Force on Colorectal Cancer suggests that individuals with a single first-degree relative with colorectal cancer should begin screening at age 40, with the same screening options and intervals as average-risk individuals 1. However, optical colonoscopy remains the preferred screening method for high-risk individuals, due to its ability to detect dysplasia and remove polyps, which is critical for preventing colorectal cancer in this population.
From the Research
CT Colonography as a Screening Option
- CT colonography can be used as a screening option for patients with a high risk of colon cancer due to family history, as it has been shown to be effective in detecting colorectal polyps and cancer 2.
- The study found that the frequency of nondiminutive polyps (≥ 6 mm) was higher in patients with a family history of colorectal cancer, but the frequencies of advanced adenoma, nonadvanced adenoma, and cancer were not significantly increased 2.
- CT colonography has been compared to conventional colonoscopy in asymptomatic average-risk patients, and it has been found to be sensitive and specific for detecting polyps 10 mm or larger 3.
Comparison with Colonoscopy
- CT colonography has been proposed as an alternative to optical colonoscopy (OC) for high-risk or very high-risk individuals, as it is less invasive and has a lower risk of complications 4.
- The study found that CT colonography can detect polyps and cancer with a high degree of sensitivity and specificity, although the sensitivity for detecting smaller polyps is decreased 3.
- CT colonography can be used in case of failure, additional risk factors, or refusal of optical colonoscopy in high-risk patients, or in the presence of a positive fecal occult blood test (FOBT) 4.
Diagnostic Accuracy
- The diagnostic accuracy of CT colonography has been evaluated in several studies, with reported sensitivities ranging from 55-94% and specificities ranging from 92-98% for polyps ≥ 10 mm 5.
- The study found that CT colonography can detect polyps and cancer with a high degree of accuracy, although the accuracy may be influenced by factors such as patient preparation and technique 5.
- CT colonography has been found to be a useful tool for distinguishing between true polyps and false polyps, with a variety of techniques and observations available to increase specificity 6.