What tests are used to diagnose colorectal (colon) cancer?

From the Guidelines

Colonoscopy every 10 years is the recommended test for screening for colon cancer in average-risk individuals, as it allows for the detection and removal of polyps before they become cancerous, and has been shown to have greater estimated life-years gained compared to other screening tests. When considering the options for colon cancer screening, it's essential to weigh the benefits and limitations of each test. The US Preventive Services Task Force recommends colonoscopy every 10 years, CT colonography every 5 years, or a stool-based test every 1 to 3 years for average-risk individuals 1. Other options include flexible sigmoidoscopy every 5 years, which examines the lower part of the colon, and stool DNA tests like Cologuard, recommended every three years 1. However, colonoscopy is considered the gold standard due to its ability to detect and remove polyps throughout the entire colon, reducing the risk of colon cancer. For individuals with higher risk factors, such as a family history of colorectal cancer or personal history of inflammatory bowel disease, screening may need to begin earlier and occur more frequently 1. Ultimately, the choice of test depends on individual risk factors, personal preferences, and availability, but regular screening is essential for early detection and improved treatment outcomes. Key considerations when selecting a screening test include the test's sensitivity, specificity, and potential risks, as well as the individual's medical history and risk factors 1. By prioritizing colonoscopy as the primary screening test, healthcare providers can help reduce the incidence and mortality of colon cancer. Some of the benefits of colonoscopy include:

• Detection and removal of polyps throughout the entire colon
• Greater estimated life-years gained compared to other screening tests
• Ability to reduce the risk of colon cancer
• Recommendation by the US Preventive Services Task Force as a primary screening test 1. However, it's crucial to consider the potential risks and limitations of colonoscopy, including:
• Bleeding or perforation of the colon
• Discomfort or pain during the procedure
• Requirement for bowel preparation and sedation
• Potential for false-negative results 1. Despite these limitations, colonoscopy remains the most effective screening test for colon cancer, and its benefits outweigh the risks for average-risk individuals. In real-life clinical practice, healthcare providers should prioritize colonoscopy as the primary screening test for colon cancer, while also considering alternative tests for individuals with specific risk factors or preferences. By doing so, healthcare providers can help reduce the incidence and mortality of colon cancer, and improve treatment outcomes for patients. The most recent and highest-quality study supports the use of colonoscopy as the primary screening test for colon cancer 1. Therefore, healthcare providers should recommend colonoscopy every 10 years for average-risk individuals, starting at age 45, to reduce the risk of colon cancer and improve treatment outcomes.

From the Research

Screening Tests for Colon Cancer

• The U.S. Multi-Society Task Force on Colorectal Cancer recommends colonoscopy every 10 years and annual fecal immunochemical test (FIT) as the first-tier tests for colon cancer screening 2.
• The second-tier tests include CT colonography every 5 years, the FIT-fecal DNA test every 3 years, and flexible sigmoidoscopy every 5 to 10 years 2.
• A systematic review of colorectal cancer guidelines suggests that colonoscopy, FIT, and CT colonography are frequently recommended screening modalities 3.

Screening Intervals and Starting Age

• The recommended screening interval for colonoscopy is every 10 years for average-risk individuals and every 5-10 years for high-risk individuals 3.
• FIT is recommended annually for average-risk individuals and every 1-2 years for high-risk individuals 3.
• Screening should begin at age 50 years in average-risk persons, except in African Americans in whom limited evidence supports screening at 45 years 2.
• Individuals with a family history of CRC or a documented advanced adenoma in a first-degree relative should undergo screening by colonoscopy every 5 years, beginning 10 years before the age at diagnosis of the youngest affected relative or age 40, whichever is earlier 2.

Risk-Stratified Approach

• A risk-stratified approach is appropriate, with FIT screening in populations with an estimated low prevalence of advanced neoplasia and colonoscopy screening in high prevalence populations 2.
• Individuals with different family histories of CRC attain the equivalent 0.44% risk of developing CRC 3-29 years earlier than their peers in the general population without such a family history 4.
• Risk-adapted starting ages of CRC screening for close or distant relatives of patients with CRC can be determined using high-quality nationwide data sets 4.

Comparative Effectiveness of Screening Tests

• The CONFIRM Study is a large, pragmatic, multicenter, randomized, parallel group trial to compare screening with colonoscopy vs. the annual fecal immunochemical test (FIT) in 50,000 average risk individuals 5.
• The study examines whether screening colonoscopy will be superior to a FIT-based screening program in the prevention of CRC mortality measured over 10 years 5.