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Colorectal (Bowel) Cancer

What is colorectal cancer?

Five percent of Australians are affected by colorectal cancer (also referred to simply as 'bowel cancer') at some stage in their life. Most colorectal cancer develops in the rectum or the sigmoid colon - the lower part of the bowel. Colorectal cancer affecting the upper parts – the caecum and the ascending colon – is slightly less common.

What causes colorectal cancer?

Medical science does not fully understand the exact cause, or causes of colorectal cancer, however it is linked to a number of diet and lifestyle factors which together increase the likelihood of any one individual developing the condition.

These risk factors for colorectal cancer include:


Women are marginally less likely to develop colorectal cancer than men.

Incidence in close relatives

This is a risk factor especially where one or more close family members have had colorectal cancer and/or where they have developed the condition at an early age.


Colorectal cancer risk increases from the age of fifty.

Dietary Intake

A food intake high in meat and animal fat and low in fresh fruit and vegetables is a risk factor for the development of colorectal cancer.

Physical Activity

A low level of physical activity and/or a sedentary lifestyle is a risk factor for colorectal cancer.


Being either obese or overweight is a risk factor.

What are the symptoms of colorectal cancer?

Often colorectal cancer has no outward symptoms in its early stages. The following symptoms warrant further investigation in case they are caused by colorectal cancer:

  • Change to bowel habits.
  • Bleeding from the rectum / anus.
  • Abdominal pain.
  • Abdominal swelling.
  • Fatigue / tiredness (this can be associated with bleeding in the bowel which in turn causes anaemia).
  • Weight loss (where this is otherwise unexplained).

How is colorectal cancer diagnosed?

Colorectal cancer generally develops over a period of time, where a polyp becomes malignant. During a colonoscopy examination any polyps found are generally removed and sent for testing to determine if they are pre-cancerous or cancerous.

As the risk of developing colorectal cancer increases over the age of 50, a special test called a Faecal Occult Blood Test (FOBT) is recommended on a regular basis for everyone over this age, even when no other risk factors are involved. Any detection of even very small amounts of blood in the stool should be investigated via colonoscopy.

Where colorectal cancer has developed, the primary treatment is surgery.