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Primary Care

Presentation: Patient with a family history of bowel cancer

A family history of bowel cancer is a significant risk factor for patients. As a clinician, taking an accurate family history is an essential part of assessing your patient’s risk.

At a glance:

  • Bowel cancer is the fourth most common cancer in the UK, with 29% of the population having a family history in a first- or second-degree relative.
  • Heritable factors are believed to account for about 35% of bowel cancer risk, but only 5%–6% of bowel cancers are a result of a monogenic inherited cancer predisposition syndrome.
  • Bowel cancer is the second biggest cancer killer in the UK, accounting for more than 17,000 deaths per year. Identifying those at increased risk allows for tailored screening with risk-reduction and earlier diagnosis, leading to improved outcomes and better survival rates.
  • Alert! Individuals with a family history of bowel cancer who are at above-population risk (either moderate or high) should be referred to specialist secondary care services.

Example clinical scenario

A 25-year-old patient contacts you because their 52-year-old father has recently been diagnosed with bowel cancer. Their father’s brother was diagnosed with bowel cancer a few years prior at the age of 54. Your patient is concerned about their own future bowel cancer risk.

Identifying those at risk of a genetic condition

  • Only 5%–6% of bowel cancer cases are associated with constitutional (germline) pathogenic variants that cause an inherited cancer predisposition syndrome.
  • The most common hereditary bowel cancer predisposition syndrome is Lynch syndrome (formerly known as hereditary non-polyposis colorectal cancer). Another hereditary cause of bowel cancer, associated with high polyp burden, is familial adenomatous polyposis (FAP). Both syndromes substantially increase the risk of bowel cancer, with FAP carrying a lifetime risk of close to 100%.
  • Rarer polyposis syndromes that also increase an individual’s bowel cancer risk include MUTYH-associated polyposis, juvenile polyposis syndrome, Peutz-Jeghers syndrome and serrated polyposis syndrome.
  • Even when hereditary bowel cancer syndromes have not been identified, if a patient has a family history of bowel cancer, they themselves carry an increased risk of up to six times that of the general population.
  • Underlying flags for a genetic diagnosis include:
    • cancer diagnosis at an early age;
    • multiple affected family members (two or more first-degree relatives or one first-degree relative diagnosed at under 50 years of age);
    • personal or family history of bowel polyps at an early age; and
    • presence of other associated cancers such as endometrial, ovarian, upper gastro-intestinal including pancreatic, gastric, small bowel and bile duct, urinary tract including renal or brain.

What do you need to do?

  • Take an accurate family history, enquiring about first- and second-degree relatives.
  • Where a family history of bowel cancer exists, the patient should have their own bowel cancer risk determined (see table 1).
  • Refer individuals at moderate or high risk to secondary care services, such as clinical genetics and/or gastroenterology.
  • Refer individuals with a known family history of inherited bowel cancer predisposition syndrome and/or known familial variant to clinical genetics services.
  • Management in primary care includes:
    • advising patients at ‘near population risk’ to respond to invitations for the NHS Bowel Cancer Screening Programme;
    • advising patients on modifiable risk factors such as smoking, alcohol consumption, weight, exercise and a healthy diet;
    • providing information on what symptoms to look out for; and
    • reporting any suspicious symptoms for early clinical assessment and examination where appropriate.
  • For information about how to arrange testing in Wales, Scotland or Northern Ireland, see our dedicated Knowledge Hub resource.
  • Information about patient eligibility and test indications were correct at the time of writing. When requesting a test, please refer to the National Genomic Test Directory to confirm the right test for your patient.

Table 1: Risk categories in patients with a family history of bowel cancer and their associated British Society of Gastroenterology (BSG) guidance

Risk Criteria BSG guidance
Average risk No family history or a family history that does not fulfil moderate- or high-risk categories. National screening
Moderate risk One first-degree relative with bowel cancer below age 50 or two first-degree relatives (in first-degree kinship) who have been diagnosed with bowel cancer at any age, where the patient under assessment is a first-degree relative of at least one affected individual. Colonoscopy at age 55
High risk Three first-degree relatives with bowel cancer diagnosed at any age, across at least two generations, where the patient is a first-degree relative of at least one affected individual. Colonoscopy every five years from age 40

 

Resources

For clinicians

References:

For patients

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  • Last reviewed: 20/01/2025
  • Next review due: 20/01/2026
  • Authors: Dr Steven Bunce
  • Reviewers: Dr Asma Hamad, Dr Jude Hayward

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