Bowel Cancer

What is Bowel Cancer?

Bowel cancer, or colorectal cancer, can affect any part of the colon or rectum. The colon and rectum form parts of the large intestine. Most bowel cancers start as benign, non-threatening growths – called ‘polyps’ – on the wall or lining of the bowel. Over time, some of these polyps can grow and become cancerous (malignant), turning into a bowel cancer. In advanced cases, the bowel cancer can spread (metastasise) to other organs of the body.

How common is Bowel Cancer?

Bowel cancer is the second most common cancer in both men and women in Australia. It is more common in people over the age of 50. Approximately 1 in 13 Australians will develop bowel cancer in their lifetime.

What are some common symptoms of Bowel Cancer?

Some of the common symptoms of bowel cancer include:

  • Blood in the stools
  • Change in bowel habits with diarrhoea, constipation, or a feeling of incomplete emptying
  • Abdominal pain
  • Weight loss
  • Loss of appetite
  • Unexplained anaemia, particularly if iron deficient

Risk factors

Several risk factors have been identified that may increase the chance of developing bowel cancer. They include:

  • Age over 50
  • Excess body fat
  • Physical inactivity
  • Smoking
  • High intake of particular foods such as processed meat
  • High alcohol consumption
  • Family history of bowel cancer
  • Inflammatory bowel disease

Screening for Bowel Cancer

Bowel cancer may be present for many years before a person develops symptoms. Some of these symptoms, such as visible bleeding in the stools, may occur after the cancer has grown and reached a relatively advanced stage. However, non-visible bleeding of the bowel may have been occurring in the pre-cancerous stage, and hence screening is important at detecting these lesions earlier.

A common method of screening for bowel cancer is performing the faecal occult blood test (FOBT). This is a non-invasive test that can detect microscopic amounts of blood in your bowel motion. It is used in the National Bowel Cancer Screening Program (NBCSP) which is funded by the Australian government. If a person has a positive FOBT, it is critical they have a colonoscopy.

Screening via a FOBT is recommended every 2 years from age 50 until the age of 74 for all individuals. Over 90% of bowel cancers can be treated successfully if detected early via screening.

Should I have a colonoscopy?

A colonoscopy is a very useful test to examine the bowel. The National Health and Medical Research Council (NHMRC) have specific guidelines in order for patients to qualify for a colonoscopy. Reasons to have a colonoscopy include:

  • Positive FOBT
  • Symptoms related to the lining of the colon, such as diarrhoea
  • If you have blood tests that show you have anaemia or iron deficiency
  • If you have imaging tests (such as a CT scan) that show a problem of the colon
  • If you had particular types of polyps removed in a previous colonoscopy
  • If you have inflammatory bowel disease (Crohn’s disease or ulcerative colitis)

The NHMRC guidelines do not recommend a colonoscopy for patients at ‘average’ risk of bowel cancer who do not have symptoms or a positive FOBT. You are at ‘average’ risk if you do not have a strong family history of bowel cancer or don’t have familial conditions that puts you at a higher risk of bowel cancer.

What if I have a family history?

About 30% of bowel cancers can be attributed to a hereditary component. If you have a family history of bowel cancer, you likely have a higher risk of developing bowel cancer yourself depending on how many of your relatives had bowel cancer and at what age they were diagnosed. Screening may need to start earlier if there is a strong history of bowel cancer, such as multiple relatives affected or if these relatives were diagnosed at a younger age.

How is Bowel Cancer diagnosed?

Your doctor will take a medical history to identify symptoms and risk factors, including your family history.  A physical examination should be performed that includes feeling your abdomen for masses or enlarged organs, and a digital rectal exam that involves the insertion of a gloved finger into the anus to feel for any abnormal growths. Blood tests are useful to assess for anaemia or low iron levels.

If you have symptoms that might be from bowel cancer, or if the screening FOBT is positive, then the main test to diagnose bowel cancer is a colonoscopy. A thin, flexible tube with a small camera on the end is inserted into the anus and used to examine the colon. If there is an abnormal growth suspicious for bowel cancer, then samples (biopsies) can be taken of the growth to confirm if it is a bowel cancer.

If bowel cancer is diagnosed, further tests will occur to assess if the cancer has spread. This involves imaging tests such as a CT scan, PET scan or MRI scan.

Further Information


The prognosis, or how long an individual will live after being diagnosed with bowel cancer, is affected by many factors including characteristics of the individual (for example their age and other health problems) and if the cancer has spread to other organs of the body.

The 5-year survival rate for bowel cancer is approximately 70%. That means approximately 7 out of 10 people with bowel cancer will be alive after 5 years from diagnosis. However if the bowel cancer is diagnosed early and has not spread outside of the bowel wall lining, then the 5-year survival is approximately 99%. That is why screening for bowel cancer is so important.


The treatment of bowel cancer may differ between individuals depending on the size, location and spread of the cancer. The main treatment options available include surgery, chemotherapy, radiation therapy or a combination of these therapies.

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