Bowel cancer

Description, causes, prevention, treatment and medicines

Bowel cancer is the second most common type of cancer affecting both men and women in Australia. Bowel cancer is cancer that starts in the large bowel (colon) or rectum, and is also known as colorectal cancer.


Change in bowel habit

Most people are aware of their usual bowel habit. For many this will mean they open their bowels once a day, for others it might be twice a day and for some it may be only 2 or 3 times a week. All of these patterns can be perfectly normal. It is when there is a change to this predictable pattern that attention is needed.

The change in bowel habit can take any form. Bowel actions might become more frequent or less frequent. They may seem looser (runny/diarrhoea), thinner or harder, or may contain mucus. Constipation (abnormally infrequent bowel motions and/or pain or difficulty when passing small, hard stools) may develop. The important thing is that there is a change. Any change that continues for more than a week or 2 and can’t be explained by a significant change in diet or medication, should be reported to a doctor.


Bowel cancer can cause bleeding into the bowel. Blood may be mixed with the bowel motions or noticed on the toilet paper or in the toilet bowl.

Other symptoms

Abdominal pain or bloating.

A feeling that you have not completely emptied your bowel after going to the toilet.
Symptoms of anaemia (tiredness, weakness, breathlessness), which can result from undetected blood loss from the bowel.

Unexplained weight loss.

There are often no symptoms in the early stages, which is why bowel cancer screening is important. When detected early, many bowel cancers can be successfully treated.

Risk factors

Factors that can increase your risk of bowel cancer include:

  • age over 50 years;
  • a diet that is high in fat and/or heavy in red and processed meat;
  • a family history of bowel cancer or polyps (polyps are non-cancerous growth, some of which develop into cancers over time);
  • inherited genetic syndromes, such as familial adenomatous polyposis or hereditary non-polyposis colorectal cancer (also called Lynch syndrome);
  • inflammatory bowel disease (ulcerative colitis or Crohn’s disease);
  • having previously had cancer or polyps in the bowel;
  • being overweight;
  • being inactive;
  • drinking alcohol; and
  • smoking.

Testing and diagnosis

Your doctor will ask about your symptoms and perform a physical examination before suggesting any tests that may be needed to diagnose possible bowel cancer.

Various tests are used to diagnose and monitor bowel cancer, as well as work out the stage of the cancer (whether the cancer is contained in the bowel or has spread).

Colonoscopy. A long tube (colonoscope) containing a fibre-optic viewing system is used to see the inside surface of the bowel and take samples of any suspicious areas for further testing. The colonoscope can view the whole length of the large bowel, allowing a thorough examination. Polyps and some small cancers can be removed entirely during colonoscopy.
Flexible sigmoidoscopy is similar to colonoscopy, but can only examine the inside surface of the rectum and lower bowel.
CT colonography (also known as virtual colonoscopy). This imaging test may be recommended if colonoscopy is not suitable. Air is pumped into the large bowel via a thin tube in the rectum, and CT or MRI images are taken along the length of the large bowel. Tumours in the bowel can be detected, but biopsy samples cannot be taken. This test is not as accurate as colonoscopy.
Imaging tests (such as X-ray, CT or MRI) can be used to help determine whether the bowel cancer has spread to other organs.
Blood tests. A full blood count may detect iron-deficiency anaemia, which can be caused by bleeding from bowel cancer. Blood levels of carcinoembryonic antigen (CEA) – a protein made by some bowel cancers – can be monitored to determine the effectiveness of treatment and to check for recurrence.


The recommended treatment(s) for bowel cancer will depend on:

  • the size and location of the tumour;
  • whether the cancer has invaded the bowel wall, spread to local lymph nodes or other organs; and
  • your overall health.


Surgery to remove bowel cancer can be done via laparoscopic (keyhole) surgery or open surgery. Usually the section of bowel that contains the tumour is removed, along with the local lymph nodes. Sometimes small cancers that have not invaded the bowel wall can be removed during colonoscopy.

In people with bowel cancer that has spread to the liver, surgical removal of the liver tumour(s) is sometimes performed.


Chemotherapy is the use of so-called cytotoxic medicines that aim to destroy cancer cells. Chemotherapy can be used:

to shrink tumours before surgery;
following surgery to reduce the likelihood of the cancer returning; or
to help treat bowel cancer that has spread to other organs.

Radiation therapy

Radiation therapy (radiotherapy), which uses special high-energy X-rays to destroy cancer cells, is often used in the treatment of rectal cancer. It is generally used together with chemotherapy, in addition to surgical removal of rectal cancer, to help prevent cancer recurrence and improve survival.

Radiation therapy can also be used to shrink rectal tumours before surgery, and to relieve symptoms in people with bowel and rectal cancer that cannot be treated with surgery.

Biological medicines (targeted therapies)

A newer type of treatment involves the use of medicines known as monoclonal antibodies. Biological medicines are generally only used in certain people with bowel cancer that has spread to other organs. These medicines can be used alone, or in combination with chemotherapy to help improve its effectiveness.


Advanced bowel cancer is cancer that has spread from the bowel to other parts of the body. The most common areas for bowel cancer to spread to are the local lymph nodes, liver and lungs.



Bowel cancer is one of the most curable cancers when detected early. Screening for bowel cancer (testing for cancer when it is in its early stages and not causing any noticeable symptoms) has been shown to significantly improve long-term survival.

Bowel cancer screening using faecal occult blood testing (FOBT) is recommended every 2 years from the age of 50 years in most people. FOBT can detect tiny traces of blood in stool samples. It is a simple test that can be done at home and then posted to a laboratory for testing. If the FOBT detects traces of blood, further testing with a colonoscopy is recommended to determine the cause of bleeding from the bowel. While cancer is not the most common cause of a positive test, it needs to be ruled out.

You can get FOBT testing kits from your doctor or pharmacist. The National Bowel Cancer Screening Program is a government programme that offers free faecal occult blood testing. Each year, eligible people are sent a free testing kit in the mail. By 2020, free 2-yearly FOBT screening will be available to all Australians aged 50 to 74 years.

For people at increased risk of bowel cancer, more frequent screening from an earlier age may be recommended, often using colonoscopy as the initial screening test.

Lifestyle factors

Lifestyle factors that can help reduce your risk of bowel cancer include:

  • eating a diet that is high in vegetables, fruit and fibre, and low in fat and processed meats;
  • maintaining a healthy weight;
  • not smoking;
  • being active (getting about 30 to 60 minutes of physical activity each day); and
  • avoiding alcohol, or drinking in moderation (no more than 2 standard drinks per day for men or one standard drink per day for women).
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