Do you recommend CT (computed tomography) colonoscopy for colorectal cancer screening?

CT Colonography for Colorectal Cancer Screening

CT colonography is recommended as a second-tier screening option for colorectal cancer when patients decline first-tier tests like colonoscopy and FIT. 1

Tiered Approach to Colorectal Cancer Screening

First-Tier Options (Preferred)

• Colonoscopy every 10 years or annual FIT are the recommended first-line screening tests for average-risk individuals 1, 2
• These tests are considered the cornerstones of screening due to their superior effectiveness and complete colon evaluation

Second-Tier Options (When First-Tier Tests Declined)

• CT colonography every 5 years 1
• FIT-fecal DNA every 3 years
• Flexible sigmoidoscopy every 5-10 years

When to Consider CT Colonography

CT colonography is specifically recommended in the following scenarios:

• When patients refuse colonoscopy and FIT 1
• Following positive fecal occult blood test in average-risk patients 1
• After incomplete colonoscopy 1
• For patients with moderate risk (personal history of adenoma/carcinoma or first-degree family history) 1

Advantages and Limitations of CT Colonography

Advantages

• Less invasive than colonoscopy
• Does not require sedation
• Evaluates the entire colon
• High sensitivity for detecting large polyps

Limitations

• Requires bowel preparation similar to colonoscopy
• Cannot remove polyps (requires follow-up colonoscopy if polyps detected)
• Exposes patients to radiation
• May not detect flat lesions as effectively as colonoscopy
• Less evidence for mortality reduction compared to colonoscopy and FIT

Age Considerations for Screening

• Begin screening at age 45 for average-risk individuals 1, 3
• Begin at age 40 (or 10 years before youngest affected relative's diagnosis) for those with family history 1, 4
• Consider discontinuing screening at age 75 or when life expectancy is less than 10 years 1
• Screening decisions for adults 76-85 years should be individualized based on prior screening history, overall health, and preferences 1

Recent Guideline Updates

The 2021 USPSTF guidelines 1 and the 2017 U.S. Multi-Society Task Force on Colorectal Cancer 1 both place CT colonography in a second-tier category, while the 2023 American College of Physicians guidance 5 recommends against using CT colonography for screening.

Common Pitfalls to Avoid

• Don't use CT colonography as first-line screening when colonoscopy or FIT are available and acceptable to the patient
• Don't forget follow-up colonoscopy is required if polyps are detected on CT colonography
• Don't recommend CT colonography for high-risk patients with inflammatory bowel disease, genetic syndromes, or strong family history of colorectal cancer, as colonoscopy is preferred
• Don't overlook the radiation exposure associated with CT colonography, especially in younger patients who may need repeated screening

Algorithm for Colorectal Cancer Screening

1. Offer colonoscopy every 10 years or annual FIT as first-line options
2. If patient declines both first-tier options, then offer CT colonography every 5 years
3. If CT colonography is positive, proceed to diagnostic colonoscopy
4. If CT colonography is negative, repeat in 5 years

In conclusion, while CT colonography is an acceptable screening option, it should be reserved for situations where patients decline the preferred first-tier screening tests of colonoscopy and FIT, which have stronger evidence for reducing colorectal cancer mortality.