Bowel cancer screening - What is it?
In this section
Cancer screening means looking for signs of cancer in healthy people. Bowel cancer screening can find bowel cancer early, before it starts causing any symptoms. It can also prevent bowel cancer, by finding small growths called polyps that might turn into cancer if they are not removed.
Bowel cancer is one of the main causes of death from cancer in the UK.[1]
The term 'bowel cancer' includes cancers of the colon and rectum, which make up the upper and lower part of your bowel.
Bowel cancer is sometimes called colorectal cancer. The bowel turns food your body doesn't need into solid waste. The waste then leaves your body when you go to the toilet.
To find out more, see Colon cancer.
Types of screening tests
Doctors use several different tests to screen for bowel cancer. We've described the four most common tests. To learn more about these tests, see What will happen to me during my test?
Faecal occult blood test
This is where a sample of your stool is tested for blood. It is called an occult blood test because blood may be hidden in your stools (the word 'occult' can mean 'hidden'). If you have blood in your stools, it might be because you have a tumour in your bowel.
Flexible sigmoidoscopy
In this test, a doctor puts a thin, bendy tube into your back passage. This allows the doctor to look at your rectum and the lower park of your bowel.
Colonoscopy
In this test, a doctor puts a thin, bendy tube into your back passage. This is pushed up your bowel so the doctor can see all the way along it.
Barium enema
In this test, a thick white liquid is put into your rectum through a tube in your back passage. Then X-rays are taken of your bowel.
How can screening help?
Screening is used to look for cancer at a very early stage, before it starts to cause symptoms. If your doctor suggests you have screening for cancer, it doesn't mean he or she thinks you have cancer. It means you might benefit from having the screening test, in case you do have cancer.
The earlier bowel cancer is found, the more likely it is to be cured. Studies show that:[2]
- If your bowel cancer is found after it has started causing symptoms, you have a 50 percent chance of surviving for at least five years
- If your bowel cancer is found before it has started causing symptoms, you have an 80 percent chance of surviving for at least five years.
Screening doesn't just help to spot bowel cancer early. It can prevent it. Some types of screening can show up lumps called polyps in your bowel. These might turn into cancer if you don't have them removed.[3]
Polyps are harmless (doctors call them benign) lumps of cells that can grow on the wall of your bowel. You're more likely to get them as you get older.[4]
Most polyps never become cancerous. But some do, and bowel cancer almost always starts from a polyp. Doctors usually remove all polyps when they find them, to be safe. Most can be easily removed during a screening test.[5]
Screening tests don't exist for all types of cancer. When tests do exist, doctors need to be sure that their benefits are bigger than their risks before offering them to patients.
Who should have screening?
Regular screening for bowel cancer is now recommended in most of the UK for men and women over 60. People who are at high risk of bowel cancer can get tested earlier and more often.
To read more, see Who should have screening?
What are the risks?
There are some risks with the screening tests used to detect bowel cancer. These include:[6]
- Damage to your bowel. In rare cases, the lining of the bowel can get injured during sigmoidoscopy and colonoscopy tests.
- False negative results. This means you do have cancer, but the test doesn't find it. So you might dismiss symptoms of cancer and miss out on vital treatment
- False positive results. This means you don't have cancer, but the test result says you do. So you get needlessly worried and have more tests or treatment that you don't really need.
Despite these risks, doctors recommend screening for bowel cancer because there is good evidence that it offers two very important benefits:[7]
- It cuts the number of people who die from bowel cancer.
- It cuts the number of cases of bowel cancer. It probably does this by detecting polyps that would have turned cancerous if they had not been removed.
References
- Cancer Research UK. Large bowel (colorectal) cancer fact sheet. April 2005. Available at http://info.cancerresearchuk.org (accessed on 16 November 2006).
- Di Gregorio C, Benatti P, Losi L, et al. Incidence and survival of patients with Dukes A (stages T1 and T2) colorectal carcinoma: A 15-year population-based study. International Journal of Colorectal Diseases. 2005; 20: 147-154.
- Centers for Disease Control and Prevention. Colorectal cancer screening. March 2006. Available at http://www.cdc.gov/colorectalcancer (accessed on 16 May 2006).
- Medline Plus. Colorectal polyps. 2004. Available at http://www.nlm.nih.gov/medlineplus/ency/article/000266.htm (accessed on 10 October 2006).
- WebMD Medical Reference in collaboration with The Cleveland Clinic. Digestive diseases: colorectal polyps and cancer. Available at: http://www.webmd.com/content/article/90/100620.htm
- National Cancer Institute. Colorectal cancer (PDQ): risks of colorectal cancer screening. October 2005. Available at http://www.cancer.gov/cancertopics/pdq/screening/colorectal (accessed on 16 May 2006).
- Scottish Intercollegiate Guidelines Network. Management of colorectal cancer. Scottish Intercollegiate Guidelines Network guideline No. 67. 2003. Available at: http://www.sign.ac.uk/guidelines/published/numlist.html (accessed on 2 July 2007).
Glossary
- colon
- Your colon is the first 2 metres (6 feet) of your large intestine. During digestion, food travels from your stomach to your small intestine and then to your large intestine. What's not digested then leaves your body as a bowel movement.
- rectum
- The rectum is the last 15 to 20 centimetres (six to eight inches) of the large intestine, ending with the anus (where you empty your bowels from).
- X-ray
- X-rays are pictures taken of the inside of your body. They are made by passing small amounts of radiation through your body and then onto film.
- polyp
- A polyp is a growth that is found inside your body.
© BMJ Publishing Group Limited ("BMJ Group") 2007. All rights reserved
This information does not replace medical advice. If you are concerned you might have a medical problem please ask your Boots pharmacy team in your local Boots store, or see your doctor.
