At what age should an asymptomatic individual with no personal or family history of colorectal cancer (CRC) and average risk start colonoscopy screening?

Colorectal Cancer Screening Starting Age

For asymptomatic average-risk adults, begin colonoscopy screening at age 50 years, with consideration for starting at age 45 years based on individual discussion of uncertain benefits.

Primary Recommendation: Age 50 Years

The strongest evidence supports initiating colorectal cancer screening at age 50 years for average-risk individuals. 1, 2, 3

• The U.S. Multi-Society Task Force on Colorectal Cancer provides a strong recommendation with high-quality evidence for screening beginning at age 50 1, 2
• The American College of Physicians recommends starting screening at age 50 years as their primary guidance statement 4
• The USPSTF gives this an A-grade recommendation (highest level) for ages 50-75 years 1
• This age threshold has the most robust evidence demonstrating mortality reduction from colorectal cancer 2

Emerging Recommendation: Age 45 Years

Screening may be offered starting at age 45 years, though this carries weaker evidence:

• The U.S. Multi-Society Task Force suggests offering screening to ages 45-49, but this is a weak recommendation based on low-quality evidence 1, 5
• The American Cancer Society recommends age 45 as a qualified recommendation (not strong) 1
• The USPSTF provides only a B-grade recommendation for ages 45-49 (compared to A-grade for 50-75) 2
• The American College of Physicians recommends clinicians consider NOT screening ages 45-49 and discuss the uncertainty around benefits and harms 4

Rationale for Earlier Screening

The push toward age 45 is driven by:

• Rising colorectal cancer incidence in adults under 50, with a strong birth-cohort effect 2
• Similar rates of advanced neoplasia in 45-49 year-olds compared to 50-59 year-olds 1, 5
• Current incidence in 45-49 year-olds now similar to rates that previously justified screening in other populations 2

High-Risk Populations Requiring Earlier Screening

Begin screening at age 40 OR 10 years before the youngest affected relative's diagnosis, whichever comes first, for individuals with: 5, 2, 6

• Family history of colorectal cancer in a first-degree relative diagnosed before age 60 5, 6
• Two or more first-degree relatives with colorectal cancer at any age 6
• First-degree relative with advanced adenoma diagnosed before age 60 6

African Americans should begin screening at age 45 years due to higher incidence rates, though this is a weak recommendation 1, 6

Screening Test Options

First-tier options (strong recommendation, moderate-quality evidence): 1, 5, 3

• Colonoscopy every 10 years 1, 5, 3
• Annual fecal immunochemical test (FIT) 1, 3

Second-tier options for patients who decline first-tier tests: 1, 5

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

The American College of Physicians recommends selecting among FIT or high-sensitivity guaiac fecal occult blood test every 2 years, colonoscopy every 10 years, or flexible sigmoidoscopy every 10 years plus FIT every 2 years 4

When to Stop Screening

Stop screening at age 75 years for individuals up-to-date with screening who have negative prior tests, particularly colonoscopy (weak recommendation) 1, 5

• For ages 76-85 without prior screening, individualize decisions based on health status, comorbidities, and life expectancy 1
• Do not screen individuals age 86 and older as risks outweigh benefits 5
• Stop screening when life expectancy is less than 10 years 1, 4

Critical Pitfalls to Avoid

• Never delay evaluation of symptomatic individuals regardless of age, especially those with bleeding, unexplained iron deficiency anemia, or melena 5, 2
• Do not continue screening beyond age 85 when harms clearly outweigh benefits 5, 2
• Ensure all positive non-colonoscopy screening tests are followed up with timely colonoscopy 1
• Do not use single-panel guaiac FOBT during digital rectal examination due to low sensitivity 3

Practical Algorithm

For average-risk asymptomatic adults:

1. Ages 45-49: Discuss screening with emphasis on uncertain benefits; if patient desires screening after shared decision-making, offer colonoscopy or FIT 1, 4

2. Ages 50-75: Strongly recommend screening with colonoscopy every 10 years or annual FIT as first-line options 1, 4

3. Ages 76-85: Only screen if never previously screened, considering overall health and life expectancy 1, 5

4. Age 86+: Do not screen 5

For high-risk individuals: Begin at age 40 or 10 years before youngest affected relative's diagnosis, whichever is earlier 5, 2, 6