If any of your family members have bowel cancer, you might be worried about your risk of getting the disease. However, bowel cancer is common and in most cases it’s not passed down through the family.
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, such as Lynch syndrome, FAP or MAP.
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.
Around 5-10% of all bowel cancer cases are thought to be caused by a change in a known gene. 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.
Lynch syndrome causes around 3% of bowel cancer cases. 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.
Everyone diagnosed with bowel cancer should be tested for Lynch syndrome. If you haven’t been tested, speak to your doctor. Make sure you tell your doctor if you have a relative with Lynch syndrome or you have a family history of bowel cancer.
If you have been diagnosed with bowel cancer but not tested for Lynch syndrome, you should speak to your GP who can refer you to a genetics team. Bring as much information about your family history, including who in your family had bowel cancer and/or other types of cancer. This will provide your GP with a strong case of support to refer you to a geneticist.
Although it’s recommended that everyone diagnosed with bowel cancer is tested for Lynch syndrome, it doesn’t always happen. That’s why we’re calling for all hospitals to follow this guidance and are campaigning to improve the diagnosis and care of people with Lynch syndrome. You can find out more on our campaigns section of the website.
What does the test for Lynch syndrome involve?
For people who have been diagnosed with bowel cancer, testing for the condition usually involves three steps:
- Screening test. A simple screening test (known as a molecular test) can be used to test for Lynch syndrome. This test looks for changes in a special type of protein your body makes, called mismatch repair proteins.
- Genetic Counselling. Before you have genetic testing you’ll have to give your consent. Before you’re diagnosed with the condition, you’ll see a genetic counsellor who will talk through the process and offer information, advice and support.
- Genetic testing. If the screening test finds changes to the genes, you’ll be referred for full genetic testing to have your diagnosis confirmed. This involves a simple blood test. Usually this takes about six-eight weeks.
If you’re having genetic testing because you have a relative known to have Lynch syndrome, you would only need genetic counselling and a blood test.
What about my family?
If you’ve been diagnosed with Lynch syndrome, your family members may choose to have genetic testing as there is a 50% chance of your children and siblings having the condition. Speak to your doctor about having your family screened for Lynch syndrome, if you’ve been diagnosed with it.
If any of your family members have Lynch syndrome, they will be offered regular colonoscopies (to look inside the bowel) 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. They might also be offered other preventative measures, such as taking aspirin, making lifestyle changes or having surgery to remove part of the colon (colectomy). Ask your healthcare team for more information on what screening is available.
Find out more about the guidance from the National Institute for Health and Care Excellence (NICE)and the Royal College of Pathologists that recommends everyone diagnosed with bowel cancer is tested for Lynch syndrome.
Familial adenomatous polyposis (FAP)
FAP is rare and contributes to less than 1% of diagnosed bowel cancers. People with FAP have a large number of growths (polyps) in the lining of the bowel. If these are left untreated, there’s a very high chance of developing bowel cancer.
Most people with FAP have surgery to remove the colon, and sometimes the rectum, to reduce their risk of developing bowel cancer. FAP isn’t always inherited from a parent. About 25% of cases are caused by a new change in the FAP gene.
MUTYH-associated polyposis (MAP)
MAP can be passed down through families but in a different way to FAP. MAP is also rare and accounts for less than 1% of all bowel cancers.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.
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.
St Mark's Hospital has a blog about the family history of bowel cancer, that contains information for the public.
Lynch Syndrome UK is a volunteer-run organisation that raises awareness of Lynch syndrome and provides information and support.
Updated June 2019
For more videos on genetic conditions that are linked to bowel cancer, please visit our YouTube channel.