Screening Recommendations for First-Degree Relatives of Patients with Colon Cancer Diagnosed at Age 73
For a first-degree relative of someone diagnosed with colon cancer at age 73, screening should begin at age 40 using average-risk screening methods, with colonoscopy every 10 years or annual FIT as first-tier options. 1, 2
Risk Stratification Based on Age of Diagnosis
The key determinant here is that the affected relative was diagnosed at age ≥60 years, which places this individual in a lower-risk familial category compared to those with relatives diagnosed younger than 60. 1
- When the first-degree relative was diagnosed at age ≥60 years: Begin screening at age 40 using the same screening methods as average-risk individuals 1, 2
- When the first-degree relative was diagnosed at age <60 years: Begin colonoscopy at age 40 or 10 years before the age of diagnosis, whichever comes first, and repeat every 5 years 1, 2
The rationale for this age-based distinction is that the relative risk differs substantially: approximately 1.8-fold increased risk when diagnosed at ≥59 years versus 3.8-fold when diagnosed before age 45 years. 1
Recommended Screening Approach
First-Tier Screening Options (Choose One):
- Colonoscopy every 10 years starting at age 40 2
- Annual fecal immunochemical test (FIT) starting at age 40 2
Second-Tier Options (If First-Tier Declined):
- CT colonography every 5 years 2
- FIT-fecal DNA test every 3 years 2
- Flexible sigmoidoscopy every 5-10 years 2
Important Clinical Considerations
The screening interval is NOT every 5 years in this scenario. This is a common pitfall—the 5-year colonoscopy interval applies only when the affected relative was diagnosed before age 60 or when there are two or more first-degree relatives with colorectal cancer. 1, 2
The incidence of colon cancer in persons with an affected first-degree relative parallels the risk in persons with no family history but precedes it by approximately 10 years, which is why screening begins at age 40 rather than 45-50. 1, 3
Verification and Documentation
Family history information is often incomplete or inaccurate, so attempts should be made to verify the diagnosis and age of onset in the affected relative when possible. 3, 4 This verification is critical because misclassification could lead to either inadequate or excessive screening.
When to Intensify Screening
More intensive surveillance (colonoscopy every 5 years) would be warranted if: 1, 2
- The relative had been diagnosed before age 60
- There are two or more first-degree relatives with colorectal cancer at any age
- The relative had an advanced adenoma (≥1 cm, villous features, or high-grade dysplasia) diagnosed before age 60