At what age should an individual with a family history of colon cancer begin screening?

When to Begin Colon Cancer Screening with Family History

Individuals with a first-degree relative diagnosed with colorectal cancer before age 60 should begin colonoscopy screening at age 40 or 10 years before the age of their relative's diagnosis, whichever comes earlier, and repeat every 5 years. 1, 2

Risk-Stratified Screening Algorithm

High-Risk Family History (Earlier/More Intensive Screening)

One first-degree relative with CRC diagnosed before age 60:

• Begin colonoscopy at age 40 OR 10 years before relative's diagnosis age (whichever is earlier) 1, 2
• Repeat colonoscopy every 5 years 1, 2
• Example: If your mother was diagnosed at age 52, you should start screening at age 40 (not age 42) 2

Two or more first-degree relatives with CRC at any age:

• Begin colonoscopy at age 40 OR 10 years before youngest affected relative's diagnosis (whichever is earlier) 1, 2
• Repeat colonoscopy every 5 years 1, 2
• This group has 3-4 times higher risk than the general population 2

One first-degree relative with advanced adenoma diagnosed before age 60:

• Follow the same protocol as CRC diagnosed before age 60 1, 2
• Begin at age 40 or 10 years before diagnosis, repeat every 5 years 2, 3

Moderate-Risk Family History (Modified Average-Risk Screening)

One first-degree relative with CRC diagnosed at age 60 or older:

• Begin screening at age 40 (not the standard age 45) 1, 2
• Use average-risk screening options: colonoscopy every 10 years OR annual FIT 1, 2
• Risk is only modestly elevated (approximately 1.9-3.4 times higher) 4

One first-degree relative with adenomatous polyps diagnosed at age 60 or older:

• Begin screening at age 40 using average-risk options 3
• Colonoscopy every 10 years or annual FIT 3

Lower-Risk Family History (Average-Risk Screening)

Second- or third-degree relatives with CRC at any age:

• Begin colonoscopy at age 45 (standard average-risk age) 1
• Repeat every 10 years 1

Critical Considerations

Colonoscopy is the strongly preferred screening method for all individuals with first-degree relative family history because it allows complete visualization and simultaneous polyp removal in a single procedure. 2, 4 Annual FIT is acceptable only if colonoscopy is declined, though it has lower sensitivity for advanced adenomas. 2

The age 60 cutoff is critical for risk stratification. The U.S. Multi-Society Task Force explicitly distinguishes screening intensity based on whether the affected relative was diagnosed before or after age 60, as younger diagnosis age in relatives indicates substantially higher genetic risk. 2, 4

Verify family history details whenever possible because this information is often incomplete or inaccurate, and the exact age at diagnosis and number of affected relatives critically determine screening intensity. 1, 2, 4

Common Pitfalls to Avoid

Do not wait until age 45 or 50 to begin screening if you have any first-degree relative with CRC—screening should begin at age 40 at the latest, regardless of when your relative was diagnosed. 1, 2

Do not use 10-year intervals for colonoscopy if your first-degree relative was diagnosed before age 60 or if you have two or more affected first-degree relatives—these situations require 5-year intervals. 1, 2

Do not assume all family history is equal. Second-degree relatives (grandparents, aunts, uncles) do not warrant the same intensive screening as first-degree relatives (parents, siblings, children). 1

Consider genetic counseling if multiple relatives have CRC or polyps, especially if diagnosed before age 50, as this may indicate Lynch syndrome or familial adenomatous polyposis requiring even more intensive surveillance. 2

When to Stop Screening

Consider stopping screening at age 75 if you are up to date with prior negative tests, particularly colonoscopy, or when life expectancy is less than 10 years. 2, 4 However, individuals without prior screening may be considered for screening up to age 85 depending on comorbidities. 4