Who is screened for bowel cancer

Bowel cancer screening aims to detect bowel cancer at an early stage when treatment is more likely to work. In England and Northern Ireland, people aged between 60 and 69 years old are sent a stool testing kit (faecal occult blood test or FOB) every 2 years. Soon, people aged 70 to 75 will also be routinely included. The national bowel screening programme in Scotland tests people aged between 50 and 74 years. In Wales the screening programme is sending testing kits to people aged between 60 and 71 every 2 years. The programme aims to include people between the ages of 50 and 74 by 2015.

In some areas a new test called Flexi-Scope, which uses a tube to examine the inside of the bowel, is being introduced as part of the screening programme.

There is detailed information about the UK bowel screening programmes on the screening for bowel cancer page. People with some other medical conditions have a higher risk of getting bowel cancer at a younger age. They are offered screening on the NHS earlier than in the bowel screening programme. The conditions which increase the risk of bowel cancer are detailed below.

FAP stands for familial adenomatous polyposis (also called familial multiple polyposis). This is a rare disease that runs in families. It causes lots of polyps to grow in the bowel. There is a high risk that one of these polyps will become cancerous. So people with FAP have either colonoscopies or sigmoidoscopies every year, to check for cancerous polyps. People with FAP are strongly advised by specialists to have surgery to remove their large bowel by age 25. This is because there is such a high probability of getting bowel cancer if you have FAP.

You may have FAP even if there are no other cases in your family. About 1 in 4 cases (25%) develop the gene change by chance, not because they inherited it.

HNPCC stands for hereditary non polyposis colorectal cancer. This is an inherited gene fault (mutation) that increases bowel cancer risk. But you don't have lots of polyps, as people with FAP do. 

If you definitely have HNPCC, your specialist will suggest that you start screening at age 25, or 5 years before the age at which your youngest affected relative got bowel cancer. You are likely to have colonoscopies every 2 years. There is not enough evidence yet for specialists to advise having the large bowel removed to prevent bowel cancer in HNPCC. But your specialist may suggest this if you do develop bowel cancer.

Strong family history means you have several relatives diagnosed with bowel cancer, or relatives diagnosed at a particularly young age. Examples of strong family history are

• 1 first degree relative diagnosed with bowel cancer before the age of 45
• 2 first degree relatives diagnosed with bowel cancer

A first degree relative is a parent, child, or sibling (brother or sister). The affected relatives must all be on the same side of your family.

If you have a strong family history, but no FAP gene or HNPCC gene, your specialist may advise you to have a colonoscopy when you are 35 to 45 years old. If you have no polyps, you probably won’t need another colonoscopy until the age of 55. It takes many years for a polyp to develop into cancer, so more frequent colonoscopies are not necessary.

The more relatives you have with bowel cancer, or the younger the diagnosed relatives are, the higher the chance that there is a cancer gene in the family. If you think you have a strong family history of bowel cancer, talk to your GP. They may send you to your local genetics clinic, where you will see someone who specialises in looking at family histories and working out the likely risk of a particular disease. They will ask you about your family, and if necessary refer you to a bowel specialist for regular screening.

Ulcerative colitis and Crohn's disease are bowel diseases that cause inflammation and ulceration inside the bowel. You have an increased risk of bowel cancer if you've had either of these diseases affecting the whole of your large bowel for more than 8 years, or the left side of your large bowel for more than 15 years. So your specialist is likely to suggest colonoscopies every 1 to 3 years to check for cancer. The British Society of Gastroenterology guidelines recommend that you should have colonoscopies

• 3 yearly if you've had ulcerative colitis or Crohn's for between 10 and 20 years
• 2 yearly if you've had ulcerative colitis or Crohn's for between 20 and 30 years
• Yearly if you've had ulcerative colitis or Crohn's for between 30 and 40 years

If you have had polyps removed from your bowel in the past, your doctor may suggest you have a sigmoidoscopy or colonoscopy every so often. This is to pick up any more polyps before they develop into an invasive cancer. How often you have a bowel examination depends on how many polyps you've had, how big the polyps were and how abnormal the cells were. The larger the polyp and the more abnormal the cells, the greater the risk of developing cancer.

If you've had 1 or 2 polyps smaller than 1cm across, you have a slightly higher than average risk of developing bowel cancer, but it is still a very low risk. Your doctor may suggest a colonoscopy every 5 years. But if you then have a colonoscopy that finds no polyps at all, you may be able to stop this screening. 

If you've had 3 or 4 polyps, or at least one that was more than 1cm across, you have a moderate (intermediate) risk of developing bowel cancer. Your specialist will probably suggest a colonoscopy every 3 years. But if you have 2 colonoscopies one after the other (consecutively) with no polyps at all, you may be able to stop this screening. 

If you've had more than 5 polyps, or more than 3 that were bigger than 1cm across, you have a much higher than average risk of developing bowel cancer. Your specialist will advise you to have a colonoscopy every year until you stop having so many polyps. If you start to have fewer polyps at each colonoscopy, then you may be able to go down to screening every 3 years.

If you have had bowel cancer in the past, there is a risk that you could develop another primary bowel cancer. So your doctor may suggest that you have a sigmoidoscopy or a colonoscopy every few years.

If you are not at higher than average risk of bowel cancer, there is currently no screening available on the NHS for people outside the age range covered by the UK bowel screening programmes. If you want to, you can pay for screening privately. You can do this by going to a private health clinic (these are listed in your local phone book). But you should check their reputation with your GP first.

Chemists have kits on sale that you can use to test your bowel motions for blood. These vary in how well they work, so you should read and follow the instructions carefully. Remember that

• 9 out of 10 people who have a test indicating blood in the stool do not have cancer
• Your result may show no blood in the stool, but you could still have a bowel cancer that was not bleeding when you did the test

So using a kit on your own is not very reliable, even if you follow the instructions carefully. Talk to your GP about why you feel you should be screened. Your GP may be able to put your mind at rest or refer you to a family cancer clinic. If you do want to use a kit like this, ask your local chemist about what is available and get their advice on how to use it.