Bowel cancer is the fourth most common cancer in the UK. Around 42,000 people are diagnosed with the condition every year. If someone in your family is diagnosed with bowel cancer or has had the disease, understandably you may be worried about developing it yourself.
Just under a third (30%) of bowel cancers are believed to be caused by a genetic fault or change and these changed genes can be passed down through a family.
Having one of these changed genes doesn’t automatically mean you will develop bowel cancer, however, it does place you at higher risk so it is helpful to be aware so you can take preventative measures.
Scientists are not completely sure which genes are responsible for bowel cancer in every case but we do know that around one in 20 of these cancers is caused by a recognised genetic change. If you believe you may be at high risk of inherited bowel cancer it is important to talk to your family about the risks so they are aware of the dangers and can make their own choices about getting tested and undergoing cancer screening.
Some genetic conditions mean you have a much higher risk of developing bowel cancer. If you have one of these conditions you are likely to have been diagnosed at an early age and you will be invited to attend for regular screening. They include:
- Lynch syndrome: This causes one in every 30 bowel cancers. Women with the condition have a slightly higher risk of ovarian cancer and both men and women are at greater risk of developing cancers in other parts of the body, including the stomach, pancreas and brain. If you have Lynch syndrome there is a one in two chance of your children, brothers or sisters having the condition so you may wish to arrange for genetic testing. If a diagnosis is confirmed they will be offered regular colonoscopies from the age of 25. This is the most effective way of monitoring for the early signs of bowel cancer (see below). The doctor may also suggest other preventative measures including lifestyle changes, surgery to remove part of the colon or taking aspirin.
- Familial Adenomatous Polyposis (FAP): FAP causes a large number of polyps to grow in the lining of the bowel. These polyps have a very high risk of developing into bowel cancer. As a result, most people with FAP have surgery to remove their colon and often their rectum as well. A quarter of cases of FAP are caused by a sudden mutation in the FAP gene rather than an inherited fault.
- MUTYH-associated Polyposis (MAP): MAP has similar symptoms to FAP but it develops as a result of inheriting two faulty genes, one from each parent. Although your parents may not have MAP themselves, they each carry a copy of the faulty gene.
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Genetic testing is increasingly popular as a way of predicting your likely risk of bowel cancer. You are most likely to be at risk if you have a parent, brother, sister or child who was diagnosed with the disease before the age of 50; or if two or more close relatives (siblings, parents, children) were diagnosed at any age; or if you have a relative with a genetic condition that is known to be linked to bowel cancer.
Regular colonoscopies are the most effective way of screening for bowel cancer. The disease develops from growths called polyps that develop in the bowel.
Over time, these growths can become cancerous. A colonoscopy allows the doctor to look inside your bowel for these polyps. If any are detected they can be removed either before they become cancerous or while they are in the early stages before cancer has an opportunity to spread to other parts of your body.