What is bowel cancer?

Bowel cancer is cancer in any part of the large bowel (colon or rectum). It is sometimes known as colorectal cancer and may be called colon cancer, depending on where it starts. Cancer of the small bowel is very rare – it is called small bowel cancer or small intestine cancer. Bowel cancer grows from the inner lining of the bowel (mucosa). It usually develops from small growths on the bowel wall called polyps. Most polyps are harmless (benign) but some become cancerous (malignant) over time.

How common is bowel cancer?

Bowel cancer is the third most common cancer affecting people in Australia. About 3,000 people in Queensland are diagnosed with bowel cancer every year. About one in 21 men and one in 31 women will develop bowel cancer before the age of 75. Bowel cancer is most common in people over 50, but it can occur at any age.

Risk factors

The exact cause of bowel cancer is not known. However research shows that people with certain risk factors are more likely to develop bowel cancer.

Risk factors include:

  • Older age – most people with bowel cancer are over 50, and the risk increases with age.
  • Polyps – having a large number of polyps in the bowel.
  • Bowel diseases – people who have an inflammatory bowel disease, such as Crohn’s disease or ulcerative colitis, have a significantly increased risk, particularly if they have had it for more than 8 years.
  • Lifestyle factors – being overweight, having a diet high in red meat or processed meats such as salami or ham, drinking alcohol or smoking.
  • Strong family history – a small number of bowel cancers run in families. If one or more of your close family members (such as a parent or sibling) have had bowel cancer, it may increase your risk.
  • Other diseases – people who have had bowel cancer once are more likely to develop a second bowel cancer; some people who have had ovarian or endometrial (uterine) cancer may have an increased risk of bowel cancer.
  • Rare genetic disorders – a small number of bowel cancers are associated with an inherited gene. These faulty genes cause a small number (about 5-6%) of bowel cancers. They are familial adenomatous polyposis (FAP) and Lynch syndrome.


Some people have no symptoms, and the cancer is found through screening. However, many people with bowel cancer do experience symptoms. These can include:

  • Blood in the stools or on the toilet paper.
  • A change in bowel habit, such as diarrhoea, constipation, or smaller, more frequent bowel movements.
  • A change in look of faeces (e.g. narrower or with mucus).
  • A feeling of fullness or bloating in the abdomen (belly) or a strange sensation in the rectum, often during a bowel movement.
  • A feeling that the bowel hasn’t emptied completely.
  • Losing weight loss for no obvious reason.
  • Weakness or fatigue.
  • Rectal or anal pain.
  • A lump in the rectum or anus.
  • Abdominal pain or swelling.
  • A low red blood cell count (anaemia or iron deficiency), which can cause tiredness and weakness.
  • Rarely, a blockage in the bowel

Most people with these symptoms don’t have bowel cancer. These symptoms can be caused by other conditions, such as haemorrhoids, diverticulitis (inflammation of pouches in the bowel), inflammatory bowel disease, or an anal fissure (cracks in the skin lining of the anus_). If you have any bleeding or other symptoms, see your doctor for a check-up.


Some people have tests for bowel cancer because they have symptoms. Others may not have any symptoms, but have a strong family history of bowel cancer or have received a positive result through the National Bowel Cancer Screening Program

General tests:

  • Physical examination – your doctor will examine your body, feeling your abdomen for any swelling.
  • Blood test – to assess your general health and to look for signs that suggest you are losing blood in your faeces (stools or poo).
  • Colonoscopy – a flexible tube with a camera on the end, called an endoscope, is inserted into your anus and up into your rectum and colon to examine the whole length of the large bowel.

Less commonly used tests:

  • CT colonography – this uses a CT scanner to create images of the colon or rectum and displays them on a screen. It is also called virtual colonoscopy.
  • Flexible sigmoidoscopy – blows carbon dioxide or air into the bowel to inflate it slightly and allow the doctor to see the bowel wall more clearly.

Further tests include:

  • CEA blood test – tests your blood for a protein called carninoembryonic antigen (CEA) which is produced by some cancer cells.
  • CT scan – uses x-ray beams to create cross-sectional pictures of the inside of your body.
  • MRI scan – uses a powerful magnet and radio waves to create detailed cross-sectional pictures of the body.
  • PET-CT Scan – injection of glucose solution containing a small amount of radioactive material to highlight abnormal tissues in the body combined with a CT scan.

Some tests may be repeated during or after treatment to check how well the treatment is working. It may take up to a week to receive your test results. If you feel anxious while waiting for test results, it may help to talk to a friend or family member or call Cancer Council 13 11 20 for support


Treatment for early and locally advanced bowel cancer will depend on the type of bowel cancer you have. This is because colon cancer and rectal cancer are treated differently.

Your medical team will recommend a treatment based on:

  • What will give you the best outcome
  • Where the cancer is in the bowel
  • Whether and how cancer has spread
  • Your general health
  • Your preferences

The most common treatment for bowel cancer is surgery. There are different types of surgery for bowel cancer. The aim of surgery for bowel cancer is to remove as much of the cancer as possible and nearby lymph nodes.

You also may need to have chemotherapy and radiation therapy.


Prognosis means the expected outcome of a disease. You may wish to discuss your prognosis and treatment options with your doctor, but it is not possible for any doctor to predict the exact course of your disease.

To come up with a prognosis, your doctor will consider;

  • Test results
  • The type of cancer you have
  • The rate and depth of tumour growth
  • The likelihood of response to treatment
  • Other factors such as age, level of fitness and medical history.

Generally, the earlier that bowel cancer is diagnosed, the better the chances of successful treatment. If the cancer is found after it has spread beyond the bowel to other parts of the body, it may still respond well to treatment can often be kept under control.

Support for Queenslanders

Whether you have been diagnosed with bowel cancer, or have a family member or friend who is affected by cancer, there are times when you may need support. Our professional services and support programs are here to help you.

Find out more about:

You don’t have to face cancer alone – we’re here to help.


For more information on bowel cancer please see these resources

If you are a patient, family or friend and would like to order a hard copy of the Understanding Bowel cancer booklet, please call Cancer Council 13 11 20