Bowel cancer - What is it?
In this section
Your bowel helps to break down the food you eat. Cancer that affects this part of your body may not cause any symptoms at first. So finding out you have it can be a shock.
Parts of your bowel are called your colon and rectum. So you may hear bowel cancer called colon cancer, rectal cancer or colorectal cancer.
Every year, more than 35,000 people in the UK are diagnosed with colon or rectal cancer.[1] The cancer begins because some cells in the inside wall of the bowel start getting out of control and damage the surrounding cells. You can get treatment to try to remove or kill the cancer and stop it spreading to other parts of your body.
If you've been told you have colon or rectal cancer, you'll probably have lots of questions about your illness and what might happen to you. Learning about your disease may reassure you and help you cope.
Key points for people with bowel cancer
- When you first get bowel cancer, you may not have any symptoms.
- Most people need surgery to get rid of the cancer.
- You may also need radiotherapy or chemotherapy.
- Anyone can get bowel cancer, but it's more common in people over 50.
- Older people can have screening tests to help spot the cancer early on. To read more, see our information on Bowel cancer screening.
People who have colon or rectal cancer say that when they have got over the shock, they find their illness has helped them focus on the things that mean a lot to them, such as their family and other important relationships.[2]
Your bowels
Your intestines are part of your digestive system. This is the group of organs that break down the food you eat. The part right below your stomach is called the small intestine or, more often, the small bowel. It's a narrow tube about 6 metres (20 feet) long (rather like a garden hose).
Your small bowel leads into your large bowel (also called the large intestine), which is about 2 metres (7 feet) long and much wider than the small bowel.
Your colon is the first 2 metres (6 feet) of your large bowel, and your rectum is the last 20 to 25 centimetres (8 to 10 inches) of your large bowel.
Bowel cancer usually grows in the large bowel. It is rare in the small bowel.
See More about your colon and rectum to learn more.
What happens if have bowel cancer?
Your bowels are mostly made of a layer of muscle. The inner lining is a thin layer of cells called the mucosa. Cells in this lining have a short life. They grow, divide in two, then die and get replaced. Your body carefully controls this activity so that cells are replaced every five days or so.
But sometimes things go wrong. Cells keep dividing when they don't need to, and old ones don't die. If this happens, you can get a cluster of extra cells called a tumour. Some tumours are made up of normal cells and they aren't dangerous. Doctors call them benign tumours. They stay put and don't cause any problems. But other tumours are made up of cancer cells. Doctors call these malignant tumours.
Cancer cells are different from healthy cells in several ways.
- They grow faster.
- They don't grow in an orderly way.
- They stay 'immature'.
- They don't stop growing when they touch other cells.
- They grow in the wrong place.
Cells in tumours can break away and move to other parts of your body. These breakaway cells are carried in your bloodstream or in your lymphatic system. When the cancer cells arrive at a different part of your body, they can start growing into another tumour. When cancer spreads like this, it's called metastasis. Blood from your bowel goes to your liver, so this is where colon and rectal cancer cells might travel.
It's hard to say why some people get colon or rectal cancer and others don't. Some kinds of cancer run in the family, but there are many other things that make it more or less likely that you'll get this kind of cancer.
See Risk factors for bowel cancer to find out more.
What are polyps?
At least two-thirds of colon and rectal cancers start inside lumps of cells called polyps. These are small growths on the inside of the bowel walls.
A polyp is a harmless, fleshy lump (a benign tumour), but it can turn into cancer (a malignant tumour).
Some doctors think that taking these polyps out makes it much less likely that you'll get colon or rectal cancer.[3] [4]
To read more, see Bowel cancer screening.
Here's what we know about polyps.
- It can take as long as 10 years for cancer to grow in a polyp. This seems to happen more quickly in the rectum than in the colon.[5]
- Some polyps are more likely than others to turn into cancer. Polyps that are less than a quarter of an inch wide are very unlikely to turn into cancer. But about half the polyps that are more than an inch wide turn into cancer.[6] The more polyps you have, the more likely it is that you'll get cancer.
- Between 30 percent to 40 percent of people in Western countries will get polyps.[7] But less than 1 in 10 of these polyps will grow into cancer.[8]
Stages of bowel cancer
Your doctor will need to find out how advanced your cancer is. This is called staging your cancer. The doctor will check how big your cancer is and how far it has spread. These tests help doctors choose the best treatment for you.
Your doctor will also look at a few of the cancer cells under a microscope. This is called grading your cancer. The more 'normal' the cells look, the less severe your cancer. If the cancer cells look very unlike normal cells, it can mean the tumour is growing quickly.
See What stage is your cancer? to read more.
References
- Cancer Research UK. Bowel cancer section overview. Available at http://www.cancerhelp.org.uk/ (accessed on 8 May 2006).
- Sahay TB, Gray RE, Fitch M. A qualitative study of patient perspectives on colorectal cancer. Cancer Practice. 2000; 8: 38-44.
- Doll R, Peto R. The causes of cancer. Oxford University Press, New York, U.S.A.; 1981.
- Colditz G. Harvard report on cancer prevention. Cancer Causes and Control. 1996; 7 (supplement): S1-S55.
- Launoy G, Smith TC, Duffy SW, et al. Colorectal cancer mass-screening: estimation of faecal occult blood test sensitivity, taking into account cancer mean sojourn time. International Journal of Cancer. 1997; 73: 220-224.
- Winawer SJ, Fletcher RH, Miller L, et al Colorectal cancer screening: clinical guidelines and rationale. Gastroenterology. 1997; 112: 594-642.
- Hardy RG, Meltzer SJ, Jankowski JA. ABC of colorectal cancer: molecular basis for risk factors. BMJ. 2000; 321: 886-889.
- Iskowitz SH, Kim YS. Colonic polyps and polyposis syndromes. In: Feldman M, Sleisenger MH, Scharschmidt BF. Sleisenger and Fordtrans gastrointestinal and liver disease: pathophysiology, diagnosis, management. 6th edition. Saunders, Philadelphia, U.S.A.; 1998.
Glossary
- lymphatic system
- The lymphatic system is the body's way of clearing and cleaning unwanted materials from the blood and tissues. It includes an interconnected network of that filter these materials to see if there is an infection that requires a response by the .
- liver
- Your liver is a large organ that sits on the right side of your body, just below your rib cage. It does several important things, including processing and storing nutrients from food, and breaking down chemicals, such as alcohol.
© 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.
