Bowel cancer is the third most common cancer in the UK for men and for women. But only a small number of bowel cancers are clearly linked to inherited cancer genes. 19 out of every 20 people (95%) with bowel cancer do not have a gene mutation running in their family.
An inherited bowel cancer gene may be more likely if there is a pattern of cancer in your family. These are examples of patterns:
- One of your first-degree relatives was diagnosed with bowel cancer before the age of 50. First-degree relatives are your parents, brothers, sisters and children.
- One of your first-degree relatives and one of their first-degree relatives were diagnosed with bowel cancer at any age (for example, your father and his sister).
- You have relatives on the same side of the family with certain types of cancer. These types of cancer include:
If you are worried about the pattern of cancer in your family, start by talking to your GP. If needed, they will refer you to a genetics specialist.
There are two main conditions caused by inherited gene mutations that are linked to bowel cancer:
Lynch syndrome (also called hereditary non-polyposis colorectal cancer, or HNPCC) can be caused by several different inherited gene mutations. People affected by Lynch syndrome have a higher risk of bowel cancer and some other types of cancer, including womb cancer.
Bowel cancer usually affects people over the age of 50. If you are diagnosed with bowel cancer before 50, there is a higher chance it may be caused by Lynch syndrome. Your doctors can test a sample of the bowel tumour for signs it was caused by Lynch syndrome. If the test shows a gene mutation is likely, you may have a genetic test to look for it.
Familial adenomatous polyposis (FAP)
FAP is caused by an inherited mutation in a gene called the APC gene. This condition causes hundreds or thousands of growths in the bowel. These growths are called polyps. They usually start to appear when a person is in their teens. If the polyps are not removed, one or more of them will almost certainly develop into cancer. Less often, FAP may also cause other types of cancer.
There are other rare inherited conditions that can increase the risk of bowel cancer. These include:
- MUTYH-associated polyposis (MAP)
- juvenile polyposis syndrome
- Peutz-Jeghers syndrome
- serrated polyposis syndrome.
Genetic Alliance UK offers information and support about rare inherited conditions.
If your family history or genetic test shows you have a higher risk of bowel cancer, there are ways to reduce that risk. This may include:
Bowel screening tests
You may be offered a test called a colonoscopy. This checks for bowel cancer or polyps that may develop into bowel cancer. Your genetics specialist will explain whether you need this test, when you should start having it and how often.
Surgery is often the most effective way to treat or prevent bowel cancer. Your doctor may talk to you about having surgery to remove an area of bowel if a colonoscopy finds changes that are very likely to develop into cancer or cancer cells.
Being aware of the symptoms of bowel cancer
Your genetics specialist can explain if there are factors in your lifestyle that affect your bowel cancer risk. Your genetics specialist, GP or practice nurse can give you more information about healthy living.