MKSAP Quiz: Colorectal cancer screening in a high-risk patient

This month's quiz asks readers to determine the best time to screen for colorectal cancer in a 38-year-old man with a family history of colon cancer diagnosed in his father at age 52 years.


A 38-year-old man is evaluated during a new-patient appointment. The patient reports no rectal bleeding or other gastrointestinal symptoms. His family history includes colon cancer diagnosed in his father at age 52 years. His personal medical history is unremarkable and he takes no medication.

All physical examination findings, including vital signs, are normal.

When should this patient undergo his first screening colonoscopy?

A. Now
B. Age 40 years
C. Age 42 years
D. Age 50 years

Reveal the Answer

MKSAP Answer and Critique

The correct answer is B. Age 40 years. This content is available to MKSAP 18 subscribers as Question 68 in the Gastroenterology and Hepatology section. More information about MKSAP is available online.

This patient should undergo his first screening colonoscopy at age 40 years. Based on the patient's family history, he is at increased risk for colon cancer. Individuals with a first-degree relative with colon cancer or an advanced adenoma diagnosed at an age younger than 60 years, or two or more first-degree relatives with colon cancer or advanced adenoma diagnosed at any age, should begin colon cancer screening at age 40 years (or 10 years earlier than the youngest age at which colon cancer was diagnosed in a first-degree relative, whichever is first). Colonoscopy, rather than imaging or stool-based testing, is the recommended screening modality. If colonoscopy is performed and findings are normal, the recommended interval for repeat screening is 5 years if the first-degree relative was younger than age 60 years at the time of diagnosis and 10 years if the first-degree relative was age 60 years or older at the time of diagnosis.

Although age 42 years is 10 years earlier than the age at which his father was diagnosed with colon cancer, guidelines recommend starting colon cancer screening at age 40 years or 10 years earlier than the family member's diagnosis, whichever comes first. Therefore, age 40 years is the appropriate age at which to begin screening in this patient.

In average-risk patients, 50 years is the recommended age to begin screening for colon cancer. Because of this patient's family history, waiting until age 50 years to begin screening for colon cancer is not appropriate.

Key Point

  • Individuals with a first-degree relative with colon cancer or an advanced adenoma diagnosed at an age younger than 60 years, or two or more first-degree relatives with colon cancer or advanced adenoma diagnosed at any age, should begin colon cancer screening at age 40 years (or 10 years earlier than the youngest age at which colon cancer was diagnosed in a first-degree relative, whichever is first).