What is bowel cancer?

Bowel cancer is the second most common cancer in both men and women and is more common in people over the age of 50.1

Bowel cancer, also known as colorectal cancer, develops from the inner lining of the bowel and is preceded by growths called polyps, which may become invasive cancer if undetected.

The risk of being diagnosed by age 85 is 1 in 11 for men and 1 in 15 for women.

Bowel cancer symptoms

Symptoms of colorectal cancer include:

  • change in bowel habit with diarrhoea, constipation or the feeling of incomplete emptying
  • thin bowel movements
  • blood in the stools
  • abdominal bloating or cramping
  • weight loss
  • fatigue
  • unexplained anaemia.

Causes of bowel cancer

There are no known causes of bowel cancer, however there are some factors that increase the risk, including:

  • inherited genetic risk and family history
  • inflammatory bowel disease
  • high red meat consumption, especially processed meats
  • being overweight or obese
  • high alcohol consumption
  • smoking.

Screening for bowel cancer

Screening, using a non-invasive test for blood in the faeces that can be done at home, is recommended for all aged 50 to 74.

Diagnosis for bowel cancer

A number of tests are used to diagnose bowel cancer, including:


The best test for bowel cancer is a colonoscopy, which examines the length of the large bowel. Air is pumped into the colon through a flexible tube that is inserted into the anus. A camera on the end of the tube allows your doctor to look for abnormal tissue that is removed for further examination.

Flexible sigmoidoscopy is used to examine the rectum and left side of the lower colon. Any unusual tissue can be removed for further examination.

CT or MRI scan

CT scans produce three-dimensional pictures of several organs at the same time and can be used to examine the bowel. An MRI scan produces detailed cross-sectional pictures of the body and can show the extent of any tumours.

Barium enema

Using a white contrasting liquid (Barium), a barium enema is a type of x-ray that will show any swellings or lumps.

PET scan

In a positron emission tomography (PET) scan, a small amount of radioactive glucose is injected into the body. When scanned, cancer cells will appear brighter.


This is a test using soundwaves that echo when something dense is encountered such as a tumour. An abdominal ultrasound is used to see if the cancer has spread to the liver whereas an endorectal ultrasound (ERUS) is done if other tests have shown cancer in the rectum or anus.

Treatment for bowel cancer


Tests that help show if you have cancer may also indicate how far the cancer has spread, which is known as staging.

Stage I is superficial, stage II is deeper and stage III is when the cancer has gone through the thickness of the wall or out into the tissues or lymph nodes beside the bowel. Stage 4 means the cancer has spread to other organs, commonly the liver.

A CT scan can be used to detect spread to the liver or lungs. A blood test to check if CEA (carcinoembryonic antigen) is elevated can be used to monitor the progress of the disease.

Types of treatment

Stage I and II disease can be treated with surgery alone to remove the bowel and surrounding lymph nodes. Stage III disease requires surgery and additional chemotherapy to try to prevent recurrence. Widespread disease is treated with chemotherapy. More recently targeted therapies are being trialled in addition to chemotherapy.

Treatment team

Your treatment team may be made up of a number of specialist staff such as:

  • colorectal surgeon who diagnoses and operates on bowel cancer
  • gastroenterologist who specialises in the digestive system
  • medical and radiation oncologists who prescribe and coordinate the course of chemotherapy and radiotherapy
  • cancer nurses
  • other allied health professionals, such as a dietitian, social worker and occupational therapist.

Prognosis for bowel cancer

An individual's prognosis depends on the type and stage of cancer, as well as their age and general health at the time of diagnosis. With stage I bowel cancer, an estimated 93% of patients will still be alive at five years. This falls to 82% with stage II, 59% with stage III and 8% for widespread disease. Across all cases, the five year survival rate for those diagnosed with bowel cancer is 66%..

Preventing bowel cancer  

The risk of bowel cancer can be reduced by not smoking, a healthy diet with plenty of fresh fruit and vegetables, and maintaining a healthy body weight.