At what age should colon cancer screening start?

Colorectal Cancer Screening Starting Age

For average-risk adults, begin colorectal cancer screening at age 45 years, with the strongest evidence supporting screening from age 50 years onward.

Screening Initiation by Age and Risk Category

Average-Risk Adults

Age 45-49 years:

• The U.S. Multi-Society Task Force on Colorectal Cancer, American Cancer Society, and USPSTF all recommend initiating screening at age 45 1, 2, 3.
• This is a qualified or conditional recommendation with lower quality evidence compared to screening at age 50 1, 2.
• The rationale is based on rising colorectal cancer incidence in younger birth cohorts, with rates in 45-49 year-olds now similar to 50-year-olds when screening was first recommended 1, 2.
• Advanced neoplasia rates in 45-49 year-olds are comparable to screening cohorts of 50-59 year-olds 2, 3.

Age 50-75 years:

• This represents a strong recommendation with high-certainty evidence 1.
• All major guidelines uniformly support screening in this age range 1.
• The net benefit of screening is substantial for mortality reduction and quality of life 1.

High-Risk Populations

African American adults:

• Begin screening at age 45 years due to higher incidence rates 1, 2, 4.
• Some older guidelines recommended age 45 specifically for this population even before the general recommendation changed 1, 5.

Family history of colorectal cancer:

• Start at age 40 years OR 10 years younger than the age at diagnosis of the youngest affected first-degree relative, whichever comes first 1, 3, 4.
• This applies when a first-degree relative was diagnosed before age 60 or when two first-degree relatives have colorectal cancer at any age 1, 4.

Lynch Syndrome or hereditary syndromes:

• Begin colonoscopy 10 years before the age at diagnosis of the youngest affected relative 3.

Screening Test Options

First-tier tests (preferred):

• Colonoscopy every 10 years 1, 2, 3
• Annual fecal immunochemical test (FIT) 1, 2, 3

Second-tier tests (acceptable alternatives):

• CT colonography every 5 years 1, 3, 4
• FIT-DNA test every 3 years 1, 3, 4
• Flexible sigmoidoscopy every 5-10 years 1, 3, 4

Evidence Quality Considerations

The recommendation to start at age 45 rather than 50 reflects evolving epidemiology but comes with important caveats:

• Limited direct screening outcome data exist for the 45-49 age group because screening at age 50 has been standard for decades 1.
• The birth cohort effect shows younger generations carrying elevated colorectal cancer risk forward as they age, with incidence increasing 1.3% per year in 40-49 year-olds 1.
• Microsimulation modeling supports benefit in 45-49 year-olds, though this is indirect evidence 1.

Common Pitfalls to Avoid

• Do not delay screening past age 50 in average-risk adults, as this carries the strongest evidence base 1, 3.
• Do not overlook family history assessment, as this substantially changes the starting age to 40 years or earlier 1, 3, 4.
• Do not continue screening beyond age 85, as harms outweigh benefits 1, 2, 3.
• Do not assume all 45-year-olds need immediate screening—while recommended, the evidence is stronger for age 50, so shared decision-making about starting at 45 versus 50 is reasonable 1.