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Many people worry about getting bowel cancer|, sometimes because a relative has had it.
Bowel cancer| is the third most common cancer in the UK for men and the second most common cancer for women. Every year more than 40,000 people will develop it. So if you just have one elderly relative who had bowel cancer, it’s unlikely that you will have a significantly increased risk.
The cause| of most bowel cancers is not known. But we do know that some things, called risk factors, can increase your chances of developing cancer. Some risk factors are very likely to cause cancer, whereas others will only slightly increase your likelihood of getting it.
Having a particular risk factor| for cancer, or being exposed to one, doesn’t mean that you will definitely get cancer - just as not having it doesn’t mean that you won’t.
We have more detailed information about the signs and symptoms| of bowel cancer, which might be helpful.
Genes carry the biological information we inherit from our parents. They affect the way our bodies grow, work and look.
Changes (mutations) in certain genes can increase the risk of bowel cancer in family members who inherit the genetic change. However, only a small number of bowel cancers are thought to be due to an inherited altered gene (genetic mutation) running in the family.
A genetic mutation that could increase your risk of developing bowel cancer is only likely to be present in your family if you have:
Only about 5 in 100 cases of bowel cancer (5%) occur in people who have a strong inherited risk.
If any of these apply to your family and you’re worried about your risk of developing bowel cancer, you may want to talk to your GP. If your GP thinks there’s a chance you may have an increased risk of developing bowel cancer because of your family history, they will refer you to a genetic counsellor|, family cancer clinic or a cancer specialist.
There are some conditions in which inherited genetic changes greatly increase the risk of bowel cancer developing:
If one of these genetic changes runs in your family, it’s likely that more than one relative on the same side of the family would have developed bowel cancer. Only about 5 in 100 cases of bowel cancer (5%) occur in people who have a strong inherited predisposition, such as Lynch syndrome or polyposis.
People who are thought to be at a higher than average risk of developing bowel cancer on the basis of their family history may be offered regular bowel screening| using a colonoscopy. A long, flexible tube is inserted gently into the back passage to look at the inside of the bowel. Bowel screening aims to detect any changes to the bowel that could develop into cancer so they can be treated and cancer prevented.
MYH associated polyposis (MAP) is a genetic condition that causes polyps to develop in the bowel. It’s caused by a fault in a tumour suppressor gene| called the MYH gene. We have two copies of each gene - one from each parent. A person needs two faulty copies of the MYH gene to be at increased risk of MAP. This makes it far less likely for children to inherit the susceptibility from their parents. Both their parents would need to carry the MYH genetic mutation, and the child would need to inherit the faulty copy from both parents.
More genes may be identified in the future, which together with factors such as diet contribute to the development of bowel cancer.
Risk factors other than family history can play a more important role in the development of bowel cancer.
The main risk factor for bowel cancer is increasing age. More than 8 in 10 people who get bowel cancer (83%) are over 60.
Some bowel conditions increase your risk of developing bowel cancer. If you have had bowel polyps (non-cancerous growths on the lining of your bowel), your risk of bowel cancer is increased. Having chronic bowel problems, such as ulcerative colitis or Crohn’s disease, also increases your risk. A doctor who specialises in bowel diseases (gastroenterologist) will assess your risk and may offer you regular screening with a colonscopy. It is important to remember that most chronic bowel problems are not bowel cancer.
A diet high in red meat and animal fat and low in fruit and vegetables increases your risk of bowel cancer.
Being overweight can increase the risk of bowel cancer developing, especially for men.
Some studies suggest that people who aren’t physically active are more likely to develop bowel cancer.
Some cancer risk factors, such as age and family history, are beyond your control.
But there are some risk factors you can control, known as lifestyle risk factors.
About 1 in 4 cancers diagnosed in the UK (25%) could be avoided if people made changes to their lifestyles.
There are a number of things you could consider to reduce your risk| of bowel cancer.
Content last reviewed: 1 April 2011
Next planned review: 2013
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If you have any questions about cancer, need support or just want someone to talk to, ask Macmillan.
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© Macmillan Cancer Support 2013
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