If any of your family members have bowel cancer, you might be worried about your risk of getting the disease. But bowel cancer is common and most people with a family history won’t need any tests or investigations.
Tell your GP if you have:
- One first degree relative (parent, brother, sister or child) diagnosed with bowel cancer before the age of 50, or
- Two or more first degree relatives diagnosed with bowel cancer at any age, or
- One or more relatives with a known genetic (inherited) condition linked to bowel cancer.
Up to a third (30 per cent) of bowel cancers may be caused by a change or fault in one or more genes. The changed gene can be passed down through a family. If you have the changed gene, you have a higher risk of getting bowel cancer at some point in your life. We don’t yet know which genes are involved in all of these cases. Around one in every 20 bowel cancers (five per cent) is caused by a change in a gene that we do know about.
The genetic conditions we know about include Lynch syndrome, Familial Adenomatous Polyposis (FAP) and MUTYH Associated Polyposis (MAP). People with these conditions have a much higher chance of developing bowel cancer and they are more likely to be diagnosed at a younger age.
Lynch syndrome used to be called hereditary non-polyposis colorectal cancer (HNPCC). It causes up to one in every 25 bowel cancers (four per cent).
Both men and women with Lynch syndrome have a higher risk of bowel cancer. Women also have a higher risk of cancer of the womb and a slightly higher risk of ovarian cancer. Men and women with Lynch syndrome also have a very slight increase in the risk of developing cancers in other parts of the body, such as the small bowel, ureter (the tube taking urine from a kidney to the bladder), stomach, pancreas, biliary tract (path carrying bile from the liver to the small bowel) and brain.
Your doctor should consider Lynch syndrome if:
- Three or more of your family members in more than two generations have bowel cancer or a Lynch syndrome-related cancer, and
- At least one of these family members was aged under 50 when they were diagnosed, and
- One of these family members is a first degree relative of the other two.
Some people with Lynch syndrome do not meet these criteria.
Guidance from the National Institute for Health and Care Excellence (NICE) recommends that everyone diagnosed with bowel cancer is tested for Lynch syndrome. Previous Royal College of Pathologists guidelines recommended only testing people under 50, NICE have expanded this to include all ages.
If you have Lynch syndrome, your family members may choose to have genetic testing. There is a one in two (50 per cent) chance of your children, brothers and sisters having Lynch syndrome.
If any of your family members have Lynch syndrome, they will be offered regular colonoscopies from the age of 25. This allows any growths (polyps) to be removed and cancer to be picked up early. Doctors do not usually start screening family members under this age because the risks of the colonoscopy are greater than the chance of picking up a cancer. Ask your healthcare team for more information on what screening is available.
Fewer than one in every 100 bowel cancers (one per cent) is caused by FAP. People with FAP have a large number of growths (polyps) in the lining of the bowel and a very high chance of developing bowel cancer. Most people with FAP have surgery to remove the colon, and sometimes the rectum, to prevent bowel cancer. FAP isn’t always inherited from a parent. About a quarter (25 per cent) of cases are caused by a new change in the FAP gene.
MAP is similar to FAP but is passed down through a family in a different way. To develop MAP, you must inherit two copies of the changed gene - one from each of your parents. Your parents may not have MAP themselves but may carry one copy of the changed gene.
If genetic testing shows you have an inherited bowel cancer syndrome, your family members may also be offered testing to see if they carry the changed gene. If they do carry the changed gene, or if there is a one in two (50 per cent) chance of them having the changed gene, they will be offered regular bowel screening.
Bowel cancer is quite common and, in most cases, genetic testing will not find any gene faults. Because of this, family members are often told they cannot have genetic testing. However, researchers continue to find out more about how bowel cancer may be inherited and more people may be able to have genetic testing in the future. If this is something you or your family are worried about, you could contact your GP or your genetics team every few years to see if anything has changed.
Find out more about our Never Too Young campaign which calls for improved identification of people with genetic conditions and access to surveillance screening.
Macmillan Cancer Support produce a booklet called Cancer genetics: how cancer sometimes runs in families. They also have an online forum for people with Lynch syndrome.
West Middlesex University Hospital has a blog about the family history of bowel cancer, that contains information for the public.
Lynch Syndrome UK
A volunteer-run organisation that raises awareness of Lynch syndrome and provides information and support.
Updated March 2016. Due for review March 2018
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