What are the recommended ages to start colon cancer screening and the appropriate intervals for average‑risk adults and for high‑risk individuals such as those with a first‑degree relative with colorectal cancer or advanced adenoma, inflammatory bowel disease, or hereditary syndromes (e.g., Lynch syndrome, familial adenomatous polyposis)?

Colorectal Cancer Screening: Age and Interval Recommendations

Average-Risk Adults

For average-risk adults, begin colorectal cancer screening at age 45 years with either colonoscopy every 10 years or annual fecal immunochemical test (FIT) as first-tier options, continuing through age 75 years. 1

Starting Age and Strength of Recommendation

• The recommendation to begin screening at age 45 is now widely adopted across major guidelines, though it carries a qualified recommendation due to limited direct outcome data in the 45-49 age group 1
• Screening from ages 50-75 years remains a strong recommendation with Grade A evidence from the USPSTF 1
• African Americans may benefit from screening starting at age 45 due to higher incidence rates and risk of advanced polyps, though this is based on weaker evidence 2, 3

First-Tier Screening Options

• Colonoscopy every 10 years is a tier-1 screening modality with the advantage of simultaneous detection and removal of polyps 1, 3
• Annual FIT is equally ranked as a tier-1 option and may be preferred in organized screening programs 1, 3
• Quality metrics matter: ensure colonoscopists have adenoma detection rates ≥25% in men, cecal intubation rates >90%, and withdrawal time ≥6 minutes 4, 2

Second-Tier Options

• CT colonography every 5 years 1
• Multitarget stool DNA test (FIT-DNA) every 3 years 1
• Flexible sigmoidoscopy every 5-10 years 1

When to Stop Screening

• Stop screening at age 75 years if up-to-date with prior negative screening tests, particularly colonoscopy 1, 2
• For ages 76-85, individualize decisions based on life expectancy, health status, and prior screening history 1
• Do not screen adults older than 85 years 1, 2

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High-Risk Individuals: Family History

For individuals with a first-degree relative diagnosed with colorectal cancer or advanced adenoma before age 60, begin colonoscopy at age 40 or 10 years before the relative's diagnosis age (whichever is earlier), and repeat every 5 years. 1, 5

Risk Stratification Algorithm Based on Family History

One First-Degree Relative with CRC Diagnosed <60 Years

• Begin colonoscopy at age 40 OR 10 years before the relative's diagnosis age, whichever comes first 1, 5
• Repeat colonoscopy every 5 years 1, 5
• Risk is increased 3.26 to 3.8-fold compared to average-risk individuals 5, 3

Two or More First-Degree Relatives with CRC at Any Age

• Begin colonoscopy at age 40 OR 10 years before the youngest affected relative's diagnosis, whichever is earlier 1, 5
• Repeat colonoscopy every 5 years 1, 5
• Risk is increased 4.2-fold 5

One First-Degree Relative with CRC Diagnosed ≥60 Years

• Begin screening at age 40 using average-risk screening options 1, 5
• Colonoscopy every 10 years OR annual FIT are acceptable 1, 5, 3
• Risk is only modestly elevated (1.8 to 1.88-fold) 5

First-Degree Relative with Advanced Adenoma Diagnosed <60 Years

• Follow the same protocol as CRC diagnosed before age 60 1, 5
• Begin colonoscopy at age 40 OR 10 years before diagnosis, repeat every 5 years 1, 5

Second- or Third-Degree Relatives with CRC

• Begin colonoscopy at age 45, repeat every 10 years 1, 5
• This represents only slightly elevated risk 1

Critical Caveats for Family History Screening

• Verify the exact age at diagnosis of affected relatives, as the age 60 threshold fundamentally changes screening intensity 1, 5
• Family history information is often incomplete or inaccurate—attempt to verify diagnosis and age of onset whenever possible 1, 5
• Do not use 10-year intervals if the first-degree relative was diagnosed before age 60 or if there are two or more affected first-degree relatives 5
• Colonoscopy is the strongly preferred method for all individuals with family history, not FIT or other modalities 5, 3

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High-Risk Individuals: Inflammatory Bowel Disease

For individuals with inflammatory bowel disease (ulcerative colitis or Crohn's disease), begin surveillance colonoscopy 8-10 years after symptom onset. 2

• Surveillance intervals depend on disease extent, duration, and presence of other risk factors such as primary sclerosing cholangitis 2
• This is distinct from screening and represents surveillance for dysplasia in chronically inflamed mucosa 2

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High-Risk Individuals: Hereditary Syndromes

Lynch Syndrome (Hereditary Nonpolyposis Colorectal Cancer)

Begin colonoscopy at age 20-25 years and repeat every 1-2 years. 5, 2

• If family history is known, begin 10 years before the youngest affected relative's diagnosis age 5
• Genetic counseling and testing should be offered when multiple relatives have polyps or cancer, especially if diagnosed before age 50 5, 2
• Colonoscopy intervals are every 1-2 years due to accelerated adenoma-to-carcinoma progression 5

Familial Adenomatous Polyposis (FAP)

Begin screening at age 10-12 years with annual flexible sigmoidoscopy. 5, 2

• Genetic counseling is essential for families with multiple affected relatives across generations 5, 2
• Prophylactic colectomy is often required given the near 100% lifetime cancer risk 2

When to Suspect Hereditary Syndromes

• Multiple relatives with colorectal cancer or polyps across generations 5, 2
• Early-onset disease (before age 50) in multiple family members 5, 2
• Pattern of extracolonic cancers (endometrial, ovarian, gastric, urinary tract) suggesting Lynch syndrome 5

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Common Pitfalls to Avoid

• Do not wait until age 50 to begin screening if there is any first-degree relative with CRC—screening should begin at age 40 at the latest 5
• Do not assume all family history is equal—the age 60 cutoff for affected relatives fundamentally changes screening intensity from 5-year to 10-year intervals 1, 5
• Do not use 5-year colonoscopy intervals in average-risk patients—this represents over-screening without evidence of benefit 4
• Do not continue screening beyond age 85—harms outweigh benefits in this population 1, 2
• Do not fail to verify family history details—second-degree relatives do not warrant the same intensive screening as first-degree relatives 1, 5
• Do not overlook quality metrics for colonoscopy—adenoma detection rate and cecal intubation rate directly impact screening effectiveness 4, 2