Patient information from BMJ

Bowel cancer: what is it?

Last published:Jul 24, 2020

Bowel cancer is a serious disease, but it can often be cured if it's caught early.

You can use our information to talk to your doctor about the best treatments for you.

What is bowel cancer?

The term 'bowel cancer' includes cancers of the colon and rectum, which make up the upper and lower part of your large bowel. Bowel cancer is sometimes called colorectal cancer.

Your large bowel turns food your body doesn't need into solid waste. The waste then leaves your body when you go to the toilet.

Bowel cancer starts when some of the cells in your large bowel begin to grow out of control. This can form a lump called a tumour. Cancer cells can then break off from the tumour and spread to other parts of your body and cause damage there.

What are the symptoms?

You might not get any symptoms in the early stages of bowel cancer. Some people only find out they have it when they go for a routine screening test. (To learn more, see the leaflet Bowel cancer: should I be screened?)

But some people do get symptoms. These can include:

• changes in your bowel habits that last for several weeks. For example, you may get diarrhoea or become constipated. Or your stools may be thinner than usual. This can happen if the cancer has partly blocked your bowel

• bleeding from your rectum or visible blood in your stools. If you have bleeding in your bowel, you may become anaemic. This can make you feel very tired and look pale

• severe pain in your abdomen.

If your doctor thinks you may have bowel cancer, you'll need tests. One of the main tests is called a colonoscopy.

During a colonoscopy, a specialist doctor (called a gastroenterologist) puts a tube with a camera on the end (a colonoscope) into your anus and passes it up into your rectum and colon. This allows the doctor to look for problems such as cancer.

If the doctor sees anything unusual during the test, he or she can take a sample of tissue to look at more closely. This is called a biopsy. Other tests you may have include scans, x-rays, and blood tests. 

Together, these tests can tell you for certain whether or not you have cancer. If you do have cancer, they can also help your doctor work out how advanced it is.

Your doctor might describe how advanced your cancer is by saying it's at a certain stage. For example:

• stage I bowel cancer means that it hasn't spread very far. This is the easiest stage of bowel cancer to treat

• stage II and III cancers have spread farther than stage I cancer but are usually still treatable

• stage IV (4) bowel cancer is the most advanced and is the hardest stage to treat.

What will happen to me?

Bowel cancer is a serious illness. But many people are cured with treatment. Your doctor will be able to tell you about how many people recover, on average, from the stage and type of cancer you have.

In general, the earlier you were diagnosed and the earlier the stage of your cancer, the better. But, remember, you are not a statistic. No one can say exactly what will happen to you. What we know in general is that:

• about 95 in 100 people with stage I bowel cancer are still alive five years after being diagnosed

• about 80 in 100 people with stage II bowel cancer are still alive five years after diagnosis

• for stage III bowel cancer, the number varies between about 45 and 85 in 100 people, depending on complications

• stage IV cancer is very hard to treat. Only about 8 in 100 people with stage IV bowel cancer are alive five years after diagnosis.

You'll have regular check-ups after being treated for bowel cancer. This is so your doctor can find out early if your cancer returns.

If you get any symptoms that worry you, don't wait for your next check-up. See your doctor straight away.

For more information on treatments for bowel cancer see our leaflet Bowel cancer: what treatments work?