Bowel Cancer Screening

Authored by Dr Colin Tidy , Reviewed by Dr Adrian Bonsall on | Certified by The Information Standard

Bowel (colorectal) cancer is common. The outlook (prognosis) and chance of cure are much better if this cancer is detected at an early stage rather than at a later stage. A screening programme operates in the UK for certain age groups. The aim is to offer an easy screening test to detect bowel cancer when it is at an early stage and before symptoms start. Some people outside the normal screening age who have a high risk of developing bowel cancer are offered extra screening tests.

See the separate leaflet called Colon, Rectal and Bowel Cancer (Colorectal Cancer).

Screening means looking for early signs of a particular disease in otherwise healthy people who do not have any symptoms. If certain diseases are picked up early, the disease can be cured. Bowel cancer screening aims to detect bowel cancer at an early stage when there is a good chance that treatment will cure the cancer. There are two methods of screening for bowel cancer:

The NHS bowel cancer screening programme in England is offered to people aged 55 or over, as there is a higher risk bowel cancer with increasing age:

  • In most but not yet all areas, anyone aged 55 is invited for a one-off screening with flexible sigmoidoscopy.
  • If you're between 60 and 74 years, you'll automatically be invited to use a home testing kit for an FOB test every two years.
  • If you're aged 75 or over, you can ask for a home FOB testing kit every two years by calling the bowel cancer screening helpline on 0800 707 60 60.

What does the FOB screening test involve?

Small (unnoticeable) amounts of blood in the stools (faeces) are common in people with bowel cancer. The test involves testing the faeces for hidden (occult) blood. See also the separate leaflet called Faecal Occult Blood Test.

If the faecal occult blood test is positive you will then be referred for further investigation which is usually a colonoscopy. A colonoscopy is a test in which a long, thin, flexible telescope (a colonoscope) is passed through your back passage (rectum) into your large bowel (colon). In this way the whole of your colon and rectum can be looked at in detail. An alternative to colonoscopy is a CT colonography.

There are various reasons other than bowel cancer for having a positive test. For example, some medical conditions including piles (haemorrhoids) can lead to a positive test. Most people with a positive test will NOT have bowel cancer.

Bowel cancer screening can also detect growths (polyps) on the inner lining of the bowel. These are not cancers but may develop into cancers over time. They can easily be removed, which makes it less likely that bowel cancer will develop.

Following a colonoscopy after screening:

  • About 5 in 10 people who have a colonoscopy will have a normal result.
  • About 4 in 10 will be found to have a polyp, which if removed may prevent bowel cancer from developing.
  • About 1 in 10 people will be found to have bowel cancer.

Note: a normal test result does not completely rule out bowel cancer. It is therefore important to be aware of the symptoms of bowel cancer and to see your doctor if you are concerned. 

What is flexible sigmoidoscopy?

The sigmoid colon is the final portion of the large bowel (colon) which is joined to the back passage (rectum). A flexible sigmoidoscope is a small bendy tube with an attached light source, about the thickness of a pen. See also the separate leaflet called Sigmoidoscopy.

What is screening with flexible sigmoidoscopy?

It has been proposed that a routine flexible sigmoidoscopy test should be offered to all adults around the age of 55. This is because most bowel polyps and bowel cancers develop in the rectum, sigmoid colon or lower descending colon. Bowel (colonic) polyps are small non-cancerous (benign) growths on the inside lining of the colon or rectum. They get more common as we become older. They usually cause no symptoms or problems. However, if a polyp is found, it is usually removed. This is because there is a small risk of a colonic polyp developing into a bowel cancer after several years.

The results of a large UK research study were published in 2010. The study found that people who had one routine flexible sigmoidoscopy, between the ages of 55 and 64, had a reduced risk of developing bowel cancer by about a third. This was because any polyps that were found during the test were removed. Also, the test can detect early bowel cancers that have not yet caused symptoms.

In October 2010 the Government announced that £60 million would be spent to fund a new flexible sigmoidoscopy screening programme for people in England aged over 55 years. This is currently in a trial (pilot) stage in certain screening centres in England. If it is shown to be effective, this screening test will probably become available everywhere in the UK. It is thought that, combined with the existing FOB test, a one-off flexible sigmoidoscopy at around the age of 55-60 could dramatically increase the number of lives saved from bowel cancer.

Some people have a higher than normal risk of developing bowel cancer. This is because some diseases cause an increased risk of developing bowel cancer. Also, relatives of people with certain diseases have an increased risk of developing bowel cancer. Therefore, some people are offered regular screening tests, often from a young age. The tests done are different from the regular screening programme. These groups of people offered extra screening tests include:

  • People with certain inherited conditions. These are rare conditions. They include:
    • Familial adenomatous polyposis (FAP).
    • Hereditary non-polyposis bowel cancer (HNPCC).
    • Peutz-Jeghers syndrome.
    • Juvenile polyposis syndrome.
  • Close relatives of people with FAP or HNPCC.
  • People with a strong family history of first-degree relatives (mother, father, brother, sister, child) who have had bowel cancer. In particular, if the cancer developed in a close relative under the age of 45 years.
  • People with ulcerative colitis or Crohn's disease affecting the large bowel (colon) or back passage (rectum).
  • People with a condition called acromegaly.
  • People who have had one or more bowel growths (polyps) removed.
  • People who have had bowel cancer in the past.

The age at which screening starts, the type of tests offered and the frequency of the tests depend on the level of increased risk. The different diseases and family associations mentioned above have varying levels of risk. The tests may include regular colonoscopy or some specialised scans.

If you have a disease or family history that causes an increased risk of developing bowel cancer, your doctor will advise on the type of tests recommended and their frequency. The British Society of Gastroenterology guidelines in 'Further Reading and References' below may also be of interest.

Further reading and references

  • ; British Society of Gastroenterology (May 2010 update from 2002)

  • ; NICE Clinical Guideline (March 2011)

  • ; Cancer Research UK

  • ; NICE CKS, October 2014 (UK access only)

  • ; The NHS Bowel Cancer Screening Program: current perspectives on strategies for improvement. Risk Manag Healthc Policy. 2017 Dec 410:177-187. doi: 10.2147/RMHP.S109116. eCollection 2017.

  • ; Colorectal Cancer Screening-Who, How, and When? Clin Endosc. 2018 Jan51(1):37-49. doi: 10.5946/ce.2017.141. Epub 2018 Jan 31.

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