Things to know about bowel cancer

Bowel cancer usually occurs in the large intestine (colon) or rectum and only rarely in the small intestine. This is why "bowel cancer" is usually understood to mean cancer of the large intestine or rectum. It is also known as colorectal cancer or colorectal carcinoma.


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Cancer of the large intestine and rectum is widespread and, together with lung cancer, is the third most common type of cancer in Switzerland. Around 95% of cancers of the colon and rectum develop in the intestinal mucosa. They begin as polyps which take about 10 years to develop into a cancer. If bowel cancer is detected at an early stage, it is curable in most cases. That is why early detection is very important.

Most people are over 50 years old at the time of diagnosis


Every year about 4’400 people in Switzerland are diagnosed with colorectal cancer and about 1’650 die of it.


In 2018, around 1’850’000 new cases of colorectal cancer were registered worldwide and more than 880’000 patients died of it.

How does bowel cancer start?

Most often, bowel cancer develops from benign growths of the mucous membrane on the inner lining of the colon or rectum. These growths are called polyps. Some types of polyps can change into cancer over time (usually many years), but not all polyps become cancer.

Signs and Symptoms

Colorectal carcinomas grow slowly. Over a long period of time they do not cause any problems. Once they reach a certain size, they may cause one or more of these symptoms:

  • a change in bowel habits (such as sudden diarrhea or constipation or a change between the two)
  • urge to defecate without emptying
  • rectal bleeding with bright red blood
  • blood in the stool, which might make the stool look dark brown or black
  • cramping or abdominal pain
  • weakness and fatigue
  • unintentional weight loss

Many of these symptoms can also be caused by other diseases, such as infections, hemorrhoids or irritable bowel syndrome. However, they should be checked by a doctor.

Bowel cancer risk factors

Researchers have found several factors that can increase the risk of bowel polyps or bowel cancer. Some of these are linked to personal lifestyle and therefore could often be avoided or at least reduced:

Risk factors that can be influenced:

  • overweight or obesity
  • insufficient physical activity
  • excessive consumption of red meat
  • alcohol use
  • smoking

Risk factors that cannot be influenced:

  • increasing age
  • gender (men are more frequently affected than women)
  • genetic predisposition

In the following cases there is an increased risk of bowel cancer:

  • earlier occurrence of colon polyps
  • bowel cancer or colon polyps in parents or siblings
  • presence of a chronic inflammatory bowel disease (e.g. Crohn’s disease or ulcerative colitis)

People who are at one or more of these risks may develop bowel cancer at a younger age.

Prevention of bowel cancer

There is no sure way to prevent bowel cancer. But a healthy lifestyle might help reduce the risk:

  • Keep your weight within the normal range.
  • Move sufficiently.
  • Eat little red meat, but enough food that contains a lot of dietary fibre (e.g. whole meal products, vegetables and fruit).
  • Drink little alcohol.
  • Don’t smoke.
  • Take advantage of the possibilities for early detection of bowel cancer.

Early detection of bowel cancer is important

If bowel cancer is detected at an early stage, it is curable in most cases. That is why screening is so important. The “blood-in-the-chest” test and colonoscopy are two proven methods of detecting bowel cancer and its precursors.

  • Blood in stool test
    The “blood in stool test” can be carried out independently at home. It is available from your doctor or pharmacy. The test detects even invisible traces of blood in the stool, which can be caused by bowel cancer or possible precursors of a bowel disease, the polyps. The reliability of the test is good if it is done every two years.
  • Colonoscopy
    Colonoscopy is a very reliable method of detecting bowel cancer. It involves a specialist examining the inside of the bowel with a flexible tube and a small camera. This camera transmits the images of the bowel directly to a monitor. In this way a tumor can be detected with a high degree of probability and possible polyps can be removed directly. The examination takes about 20 to 30 minutes and is usually painless.

CH-NON-00751, 08/2020