When should colon cancer screening be initiated for a 40-year-old healthy man with a first-degree relative diagnosed with colon cancer at age 50?

Colon Cancer Screening for 40-Year-Old with First-Degree Relative Diagnosed at Age 50

This patient should start colonoscopy screening now (at age 40) and repeat every 5 years (Answer B). 1

Risk Stratification

This 40-year-old man is not average-risk—he has an increased risk for colorectal cancer because his first-degree relative was diagnosed at age 50, which is before age 60. 1 This distinction is critical:

• First-degree relative diagnosed <60 years: The patient's risk is approximately 3.26 to 3.8-fold higher than the general population 1, 2
• First-degree relative diagnosed ≥60 years: Risk is only 1.8-fold higher and warrants different screening 2

The age 60 cutoff is the key decision point that determines whether 5-year or 10-year colonoscopy intervals are needed. 3

Recommended Screening Algorithm

For this patient with a first-degree relative diagnosed at age 50:

• Start colonoscopy at age 40 (which is now) 1
• Repeat colonoscopy every 5 years 1, 3
• Colonoscopy is the preferred and recommended screening method, not FIT or other alternatives 1, 3

The rationale for starting at age 40 is that colorectal cancer incidence in persons with an affected first-degree relative parallels average-risk individuals but occurs approximately 10 years earlier. 1, 2

Why Other Options Are Incorrect

• Option A (start at 50, every 10 years): This is average-risk screening and inappropriate for someone with a first-degree relative diagnosed before age 60 1
• Option C (start at 50, every 5 years): The interval is correct, but starting at age 50 is too late—he should start now at age 40 1
• Option D (annual FOBT): While annual FIT can be offered if the patient declines colonoscopy, it is not the preferred first-line recommendation for high-risk individuals 1

Critical Caveats

Verify the complete family history before finalizing the screening plan: 1

• If there are two or more first-degree relatives with colorectal cancer at any age, the same 5-year colonoscopy interval applies 1, 3
• If the relative had a documented advanced adenoma (≥1 cm, villous features, or high-grade dysplasia) diagnosed before age 60, treat it the same as colorectal cancer diagnosed before age 60 1, 3
• If multiple relatives have polyps or cancer, especially before age 50, consider genetic counseling for Lynch syndrome or familial adenomatous polyposis 1

Evidence Quality

The most recent and highest-quality guideline is the 2023 AGA Clinical Practice Update, which explicitly states that individuals with a first-degree relative diagnosed with colorectal cancer before age 60 should begin screening at age 40 and repeat every 5 years. 1 This recommendation is consistently supported across multiple major society guidelines including the U.S. Multi-Society Task Force (2017) 1 and the American College of Physicians (2012). 1