Causes and risk factors of bowel cancer
There are different risk factors that can increase your chance of developing bowel cancer.
In the UK, about 41,000 people get cancer in the large bowel each year. The large bowel includes the colon and the rectum.
The exact cause of bowel cancer is unknown. But, things called risk factors can increase the chance of a person developing it. Having one or more risk factors does not mean you will definitely get bowel cancer. And if you do not have any risk factors, it does not mean you will not get bowel cancer.
Eating a lot of red and processed meat increases the risk of bowel cancer.
Red meat includes:
Processed meat includes:
- smoked meat
- tinned meat.
Eating fried or grilled meat may also increase the risk.
Current UK guidelines recommend that you eat no more than 70g of red meat per day. That is about 3 slices of ham or 1 lamb chop. No link has been found between bowel cancer and eating poultry such as chicken and turkey, or seafood.
Not eating enough fruit and fresh vegetables may also increase the risk.
Having an inflammatory bowel condition, such as ulcerative colitis or Crohn’s disease, can increase the risk of bowel cancer.
Irritable bowel syndrome is not an inflammatory bowel condition. It does not increase the risk of getting bowel cancer.
Most people who get bowel cancer do not have a family history of it. Having one family member who developed bowel cancer at an older age does not increase your risk.
If several close family members on the same side of your family have had bowel cancer, this may increase your risk. You may also have a higher risk if a close family member had bowel cancer before the age of 50. Close family members are parents, brothers and sisters.
People who have a history of bowel cancer in their family can be referred to a specialist clinic to have their risk assessed. People at higher risk of bowel cancer are offered bowel screening with a colonoscopy. For more information, contact your GP or call our cancer support specialists on 0808 808 00 00.
Inherited (familial) conditions
About 5 in every 100 bowel cancers (5%) are caused by an inherited faulty gene.
There are two rare conditions that can run in families:
- familial adenomatous polyposis (FAP)
- Lynch syndrome (also called hereditary non-polyposis colorectal cancer or HNPCC).
People with either condition have a very high risk of developing bowel cancer.
We have information about cancer and genetics.
Bowel cancer is not infectious and cannot be passed on to other people.
Familial adenomatous polyposis (FAP)
FAP causes less than 1 in every 100 bowel cancers (less than 1%).
People with FAP have hundreds or thousands of benign tumours (polyps) in the lining of their colon. They may also have polyps in their rectum.
People with FAP have regular screening using colonoscopies to look for signs of cancer. It is usually recommended that people with FAP have an operation to remove their colon and sometimes their rectum. Unless the colon is removed, nearly everyone with FAP will develop bowel cancer.
Lynch syndrome (HNPCC)
People with Lynch syndrome have an increased risk of developing bowel cancer at a young age. Lynch syndrome causes about 4 in every 100 bowel cancers (4%).
If you have Lynch syndrome, you will usually have regular screening using colonoscopies. Screening normally starts from the age of 25. Or it may start five years before the age at which your youngest relative developed bowel cancer. The colonoscopy is usually repeated every 18 months to 2 years..
Below is a sample of the sources used in our bowel cancer information. If you would like more information about the sources we use, please contact us at firstname.lastname@example.org
R Glynne-Jones, PJ Nilson, C Aschele et al. ESMO-ESSO-ESTRO Clinical practice guidelines for diagnosis, treatment and follow up for anal cancer. July 2014. European Society of Medical Oncology. Available from www.esmo.org/Guidelines/Gastrointestinal-Cancers/Anal-Cancer (accessed October 2019).
National Institute for Health and Excellence (NICE). Colorectal cancer: diagnosis and management clinical guidelines. Updated December 2014. Available from www.nice.org.uk/guidance/cg131 (accessed October 2019).
Association of Coloproctology of Great Britain & Ireland (ACPGBI). Volume 19. Issue S1. Guidelines for the management of cancer of the colon, rectum and anus. 2017. Available from www.onlinelibrary.wiley.com/toc/14631318/19/S1 (accessed October 2019).
BMJ. Best practice colorectal cancer. Updated 2018. Available from www.bestpractice.bmj.com/topics/en-gb/258 (accessed October 2019).
This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer. It has been approved by Chief Medical Editor, Professor Tim Iveson, Consultant Medical Oncologist.
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