High risk groups for bowel cancer
This page tells you about high risk groups for bowel cancer. There is information about
How common is bowel cancer?
Bowel cancer is the 3rd most common cancer in the UK. Most are in the large bowel (colon), with less than 1 in 3 being in the back passage (rectum). In most people, the exact cause of bowel cancer is unknown. More than 8 out of 10 bowel cancers are diagnosed in people over 60.
Family history and inherited conditions
Strong family history means you have several relatives on the same side of your family diagnosed with bowel cancer, or one or more relatives diagnosed at a young age. If you think you might have a strong family history, talk to your GP. He or she may refer you to a specialist genetics service. About 1 in 20 cases of bowel cancer are caused by the inherited conditions called familial adenomatous polyposis (FAP) and hereditary non-polyposis colorectal cancer (HNPCC or Lynch syndrome). People who have Ashkenazi Jewish blood also have a higher risk of bowel cancer.
Medical conditions that increase risk
Growths in the bowel called polyps or adenomas can develop into cancer over a long period of time. Adenomas are quite common, but only a small fraction of them become cancer. Having very severe ulcerative colitis or Crohn's disease for many years increases your risk of bowel cancer. So does diabetes, though we don’t know why. You are also at higher risk of bowel cancer if you have had it before.
You can view and print the quick guides for all the pages in the About bowel cancer section.
Bowel cancer is the 3rd most common cancer in the UK after breast and lung cancer. There are about 37,500 cases diagnosed in the UK each year. About 14,000 of these are in the back passage (rectum) and the rest in the large bowel (colon).
The biggest single risk factor is age. More than 8 out of 10 bowel cancers (83%) are diagnosed in people over the age of 60. So the risk of getting this disease increases as you get older. The page about how does a cancer start explains why cancers are more likely to occur as we get older. But we think that many bowel cancers could be prevented with changes in diet and lifestyle. You can find more information about this on the pages about diet as a risk factor for bowel cancer and other lifestyle risk factors.
Strong family history usually means you have several relatives diagnosed with bowel cancer, especially if they are in different generations of your family. It can also mean you have one or more relatives diagnosed at a particularly young age. Examples of strong family history are
- 1 first degree relative diagnosed before the age of 45
- 2 first degree relatives diagnosed at any age
A first degree relative is a parent, brother or sister, son or daughter. To have a strong family history, the affected relatives must all come from the same side of your family.
If you think you might have a strong family history, you should start by going to talk it over with your GP. If your doctor agrees, you will probably be referred to a specialist genetics service. They will look into your background closely by talking about your family history with you. They will also ask you detailed questions about your families' health and illnesses. You may have blood tests as part of this investigation. If the geneticist agrees that you do have a higher than average risk of bowel cancer, you'll then see a bowel specialist to talk about having regular tests (screening) to pick up any signs of bowel cancer as early as possible. There is more information about this on the page about screening people at high risk of bowel cancer.
Two particular inherited conditions can increase the risk of bowel cancer. These are FAP and HNPCC. FAP stands for familial adenomatous polyposis. HNPCC stands for hereditary non-polyposis colorectal cancer (also called Lynch syndrome). Although these gene changes increase the risk quite a bit for people who have them, they are very rare. FAP and HNPCC together are only responsible for about 1 in 20 cases of bowel cancer (5%).
FAP
FAP (familial adenomatous polyposis) is a rare disease that runs in families. It is responsible for about 1 out of every 100 bowel cancers (1%). FAP causes lots of small non-cancerous growths (benign polyps) to develop in the large bowel (colon). But some of these can develop into cancer over a long period of time. Because people with FAP have so many polyps, they have a high risk of getting bowel cancer. By their 40's or 50's, it is almost certain they will have bowel cancer. Specialists recommend that people with FAP have surgery to have all of their colon removed by the age of 25 to prevent them getting bowel cancer. There is information about this on the page about screening people with FAP.
You can have FAP even if there are no other cases in your family. In about 1 in 4 cases, the gene mutation comes about by accident and not because you've inherited it.
HNPCC
Another rare gene fault that runs in families is Lynch syndrome or HNPCC (hereditary non-polyposis colorectal cancer). The healthy form of this gene helps DNA to repair itself. If you have the faulty gene for HNPCC, you are at a greater risk of several different cancers. The risk of bowel cancer is increased most. But there is also increased risk of womb cancer, ovarian cancer, stomach cancer, pancreatic and biliary cancer, and bladder cancer. About 9 out of 10 men (90%) and 7 out of 10 women (70%) with the HNPCC gene fault develop bowel cancer by the age of 70. If your doctor suspects you carry an HNPCC gene fault, your specialist may suggest you have surgery to try to stop bowel cancer from developing.
Because it is rare, HNPCC is probably only responsible for between 2 and 5 out of every 100 (2 to 5%) bowel cancers diagnosed. If you know a relative has this particular type of gene fault, you can be tested to see if you have it too. But at the moment, it is not possible to genetically screen the whole population.
HNPCC is particularly linked to bowel cancer that develops at a young age. It probably causes about 4 out of 10 bowel cancer cases (40%) that develop in people under 30. A Cancer Research UK study in Scotland is screening everyone under 55 who gets bowel cancer to see if they carry the gene fault. Once this study is completed, relatives of people who carry the gene can be tested. There is information about this on the page about screening people with HNPCC.
Growths in the bowel, called polyps or adenomas, are not cancerous. But they can develop into cancer over a long period of time. In fact, most bowel cancers develop from an adenoma. Adenomas are quite common. About 1 in 4 of us have one or more by age 50. About half of us have them by age 70. But only a small fraction of adenomas develop into cancer and it takes years to happen. An adenoma that is 1 cm across has roughly a 1 in 6 chance of growing into a cancer over 10 years. The bowel screening programmes in England, Wales, Scotland and Northern Ireland aim to find and remove polyps in the general population before they become cancerous. People who have gene changes that increase their risk of bowel cancer may need to have screening more often than the general population. There is more information about screening on the page about screening people at high risk of bowel cancer.
These are chronic bowel diseases. They both cause inflammation in the bowel. Having very severe ulcerative colitis or Crohn's disease that affects the large bowel for many years increases your risk of bowel cancer. Probably about 1 in every 100 cases of bowel cancer (1%) is due to ulcerative colitis. The increased cancer risk is probably because the disease damages the lining of the bowel and it has to repair itself again and again. The increase in cell turnover increases the risk that a cancerous cell might develop. You can read more about this on the page about screening people with a history of ulcerative colitis and Crohn's.
If you have already had bowel cancer, you are about 4 times more likely to get it again than the average person. Your specialist will talk to you about how often you may need screening tests. There is information about this on the page about who can be screened for bowel cancer.
If you have diabetes, your pancreas doesn't make enough of a hormone called insulin. People with diabetes have an increased risk of bowel cancer. We don't know why this is and scientists are looking into it.
People who have Ashkenazi Jewish blood have a higher risk of bowel cancer. This may be due to a gene fault that is more common in this group than in the general population. About 1 in 10 Ashkenazi Jews have a faulty gene called I1307K. We don't know yet if it is this gene that causes the increase in bowel cancer. People in this group also have a higher risk of breast cancer because they are more likely to carry one of the breast cancer gene faults - BRCA1 or BRCA2.
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