Family history

Does bowel cancer run in families?

Most people who develop bowel cancer have no family history of bowel cancer. However, for around 25% of all bowel cancer cases diagnosed in the UK there is a family history. Generally speaking, the more members of the family affected by bowel cancer, and the younger they were at diagnosis, the greater the chance of a family link.

What is my risk of hereditary bowel cancer?

The following guidelines from the British Society of Gastroenterology may help you and your GP assess your personal risk:

High to moderate risk:

  • at least 3 relatives in your family diagnosed over the age of 50 years, and over 2 generations on one side of the family, or
  • 2 close relatives in your family diagnosed under the age of 60 years, or
  • 1 immediate relative aged less than 45 at diagnosis of bowel cancer

The national guidelines in this case would be to recommend a colonoscopy at 35 years, and then follow up with a 5 year colonoscopy between ages 50 – 75 years for individuals with known risk.

Low to moderate risk:

  • 1 close relative affected under age 50 years, or
  • 2 close relatives affected over age 60 years

The national guidelines in this case would be to offer a one off colonoscopy at 55 years.

Low risk:

  • 1 close relative diagnosed at over 50 years of age and no other family history of bowel cancer or non-polyposis related cancers.

Lynch Syndrome -  hereditary non-polyposis colorectal cancer (HNPCC)

Each person inherits genes from both their parents and HNPCC is caused by a fault in one of the genes known as the 'mismatch repair' genes. Someone who inherits HNPCC from their parents has a normal gene and a 'faulty' gene, which increases their risk of developing bowel cancer and other types of cancer.

HNPCC affects less than 5% of those who develop bowel cancer. Although rare, this risk relates to a clear family history of bowel or specific, related cancers e.g. some gynaecological cancers, digestive tract, urinary tract, brain or bowel cancer. The typical age of diagnosis of this kind of hereditary hon-polyposis holon cancer (HNPCC or Lynch Syndrome) is usually between 40-50 years (compared to 60-70 years amongst the general population).

Familial adenomatous polyposis (FAP)

FAP is characterised by the presence of hundreds or thousands of adenomatous polyps in the colons of affected individuals, which  often start in adolescence. Cancerous polyps are very common in this condition, usually by age 40, without active management of the polyps and screening on a regular basis. Diagnosis is usually made following colonoscopy to confirm the presence of polyposis. Testing for mutation of the APC gene currently detects 95% of mutations present. 


In families where there is a clear history of another rare type of bowel cancer, known as Familial Adenomatous Polyposis ( FAP), screening usually commences by the age of 13 with annual sigmoidoscopy for the first few years, and then annual colonoscopy using a special dye spray. Where FAP is suspected, your GP will refer you to the local Regional Genetics Centre for support and on-going management of the condition, because it has been known to affect adolescents and teenagers.  Screening for the other complications of FAP is also possible, and the local Regional Genetics Centre will be able to advise about these on an individual basis, once they have seen you and your family in their clinic.

The treatment for FAP is usually a planned operation to remove the affected part of the colon once polyposis has become established. This normally occurs in the late teens or early twenties. These are very rare conditions and you will need the specialist help and support of an experienced colorectal team to help make the right decisions for the individual affected.

Genetic counselling

Do you know if anyone in your family has had bowel or any other kind of cancer? Talk to your family and make sure you all know your family history.

If you think you have a strong family history of bowel cancer, you should make an appointment with your GP to talk about your concerns. If your GP agrees with you, he/she will refer you to a specialist genetics service. The genetic specialist will go through your family history with you in great detail and ask you to provide accurate information about who has been affected, how old they were when they were diagnosed, and the site where their cancer developed. You may also have to have blood tests as part of this investigation.

If the genetic specialist agrees you are at increased risk, you will be referred to a bowel specialist to talk about what types of screening they recommend, at what age you (and/or other family members) should start being screened and how often you should be screened. Regular screening will ensure that any signs of bowel changes and early cancer are spotted and treated quickly.

For more information about family history and the national guidelines for screening people at higher risk of bowel cancer, please click here.

For more information about genetic testing for HNPCC, you can visit:

Genetic Health (search for colon cancer)

Macmillan Cancer Support (search for HNPCC)

More support and information for individuals affected by FAP can be found at

FAP Gene Support

Macmillan Cancer Support (search for FAP)

Last reviewed 8/1/2013Information Standard Logo

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