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Screening for Bowel (Colorectal) Cancer

Screening for Bowel (Colorectal) Cancer

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.

Bowel cancer is a cancer of the colon or rectum. When the cancer first starts to develop, there are typically no symptoms for several weeks or months. Then, as the cancer progresses, the common initial symptoms include:

  • Bleeding from the back passage (rectum).
  • Changes to your bowel habit (for example, having prolonged episodes of diarrhoea).
  • Tiredness due to low iron levels (anaemia).

See separate leaflet called Bowel (Colorectal) Cancer for more details.

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:

  • A test to detect traces of blood in your stools (faeces). This is called the faecal occult blood (FOB) test.
  • An examination of the inside of the bowel by a test called flexible sigmoidoscopy.

The first test is now offered routinely in the UK to those in the appropriate age range. The second test may well become routinely offered in the near future. Each is now discussed in more detail.

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. This test involves testing three samples of your faeces for traces of blood.

If you are in the relevant age group (see below) then you will automatically be sent an invitation and an FOB screening kit to do the test at home. After your first screening test, you will then be sent another invitation and screening kit every two years until you reach the maximum age.

The testing kit is a very simple way for you to collect small samples of your faeces in your own home. Although it sounds embarrassing and unpleasant, it is surprisingly easy and quick to actually do. There are clear instructions sent with the kit. You obtain a sample by using a small scraper to scrape some faeces off toilet tissue which you have just used after going to the toilet. You will then need to wipe very small samples of three different bowel motions on a special card. You then send the card in a hygienically sealed, prepaid envelope to a laboratory for testing. You will be sent the results of your test by post within two weeks.

The FOB test can confirm the presence of blood in faeces. However, it is unable to show where the blood is coming from or what the cause of the blood is. Bowel cancer is just one cause of blood in faeces. See also separate leaflet called Faecal Occult Blood Test.

Who is invited to do the FOB screening test?

Most cases of bowel cancer develop in people over the age of 50. Therefore, the decision has been made for people of a certain age to be invited to participate in the bowel cancer screening programme. The NHS Bowel Cancer Screening Programme has been introduced in the UK as follows:

  • In England, Wales and Northern Ireland, people aged 60 to 74 are automatically offered screening every two years. If you are aged 75 or over and wish to be screened, you can phone the helpline in your particular country to request the kit:
    • England - Helpline: 0800 707 6060
    • Wales - Helpline: 0800 294 3370
    • Northern Ireland - Helpline: 0800 015 2514
  • In Scotland, people aged 50 to 74 are routinely offered screening every two years. If you are aged 75 or over and wish to be screened, you can phone the helpline for Scotland to request the kit:
    • Scotland - Helpline: 0800 012 1833

The first test kit should automatically arrive by post within a few weeks after you reach the age in which screening starts. You can call the relevant helpline (details above) and ask for one if one does not come.

The websites of the screening programmes for each country are available via the UK screening portal (see references below) and under 'Further help & 'information', below.

What are the possible results of the screening test?

The results of the FOB test can be either:

  • Negative. That is, no blood present. This is the result for around 98 in 100 people. Routine screening will then be offered to you every two years until you reach the age when screening stops.
  • Unclear. This is the result for around 2 in 100 people. The FOB test then needs repeating.
  • Positive. That is, blood is found to be present. This is the result for around 2 in 100 people. 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.

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.

Is the FOB screening test effective?

As this screening test has only recently been introduced, it is too early to know exactly how effective it will be. However, initial statistics indicate that it is saving many lives. It is estimated that over 2,000 lives could be saved every year in the UK by 2025 due to screening with the FOB screening test.

Also, figures published in 2009 from the National Cancer Intelligence Network showed that people with bowel cancer who are diagnosed at an early stage (stage A) have more than a 9 in 10 chance of surviving the disease. Up until recently (prior to screening), only about 1 in 7 people with bowel cancer were diagnosed at stage A, as the disease does not often cause symptoms at this early stage. Until recently, most cases of bowel cancer were diagnosed when the disease was more advanced and causing symptoms. The disease is much less likely to be cured at these later stages. With the introduction of screening, many more cancers have been diagnosed at the early stage when a cure is much more likely to be possible.

So, these figures show just how important it is to diagnose the disease as early as possible for the best chance of a cure. This is exactly what bowel cancer screening is all about - to diagnose the condition early to give the best chance of a cure.

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. A doctor or nurse inserts the sigmoidoscope into the anus and pushes it slowly through the rectum to the sigmoid colon and the lower part of the descending colon. This allows the doctor or nurse to see the lining of the rectum, sigmoid colon and the lower part of the descending colon. The procedure is not usually painful but it may be a little uncomfortable. This test is similar to colonoscopy. However, colonoscopy is a more complex procedure involving a long flexible instrument that inspects the entire large bowel. If you are having a colonoscopy, you usually need an injection to make you drowsy (a sedative). Unlike colonoscopy, a flexible sigmoidoscopy can be done easily without the need for a sedative. See also separate leaflet called Sigmoidoscopy.

The Gut - simple
Large bowel showing a polyp

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 get 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 depends 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 references below may also be of interest.

Further reading & references

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but makes no warranty as to its accuracy. Consult a doctor or other healthcare professional for diagnosis and treatment of medical conditions. For details see our conditions.

Original Author:
Dr Tim Kenny
Current Version:
Dr Mary Harding
Peer Reviewer:
Dr John Cox
Document ID:
9335 (v6)
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