Australia has one of the highest rates of bowel cancer in the world. Each year, more than 16,000 Australians are diagnosed with bowel cancer. Many bowel cancers are detected at later, difficult to treat stages. If detected early, almost all cases of bowel cancer are curable. We are working to develop better early detection tests and to improve treatments for bowel cancer.

Our bowel cancer research

Our bowel cancer scientists and clinicians are working to improve the detection and treatment of bowel cancer by:

• Understanding the changes in healthy bowel cells that drive cancer formation.
• Deciphering how cancer cells 'communicate' with their environment to promote tumour growth.
• The role of bacterial infections and inflammation in cancer development.
• Developing better ways to detect and treat early-stage bowel cancer, including through a blood test.
• Discovering potential new treatments for bowel cancer.
• Matching people with bowel cancer to the best treatment for their disease.

What is bowel cancer?

Bowel cancer begins as an uncontrolled growth of cells in the walls of the bowel (the large intestine – the colon or the rectum). If untreated, the cancer can spread to other organs. Bowel cancer may also be called colon cancer or colorectal cancer.

Most bowel cancers arise from cells in the bowel lining called epithelial cells. These cells become cancerous after acquiring genetic changes that make them divide excessively and become long-lived.

Small non-cancerous growths in the bowel lining called ‘polyps’ often precede bowel cancer. Most polyps do not grow any further. Occasionally the cells in a polyp undergo changes that make them grow into a larger tumour. This can damage or block the bowel. ‘Metastatic’ or ‘secondary’ bowel cancer occurs when cancer cells spread beyond the bowel and travel to other parts of the body, where they grow as tumours.

Bowel development and cancer

Bowel cancers arise from the cells that line the bowel. They occur because the systems that normally control cell growth and survival have stopped working properly. Many processes that occur in bowel cancer cells are similar to those occurring during the development and growth of the bowel in embryos. Understanding how cell growth is controlled during bowel development is revealing what goes awry in bowel cancer.

Bowel cancer risk factors

Most bowel cancers arise ‘spontaneously’, with no predictable cause. Like many cancers, the risk of developing bowel cancer increases with age. About 92 per cent of people diagnosed with bowel cancer are over the age of 50.

Other risk factors for developing bowel cancer are:

• A history of developing polyps, or an earlier case of bowel, stomach or uterine cancer. These cancers may all be caused by similar cancer-causing gene abnormalities.
• Having relatives who had polyps or bowel cancer. People can be tested for inherited (familial) bowel cancer risk genes.
• Having inflammatory bowel disease, such as colitis or Crohn’s disease.
• A diet high in red meats, processed meats, fried foods or alcohol, or low in vegetables, fruit and whole grains.
• Being obese or physically inactive.
• Smoking.

How is bowel cancer detected?

The earliest, most treatable forms of bowel cancer generally have no symptoms. Clinical trials have shown that offering bowel cancer screening tests to people older than 50 years saves lives through early detection. Screening is a cost-effective way to detect bowel cancer at early and curable stages.

Currently, bowel cancer screening uses the faecal occult blood test (FOBT) that detects small amounts of blood in a stool (faeces) sample. Blood in stools is a possible sign of early bowel cancer.

When bowel cancer is suspected, the bowel lining can be examined by colonoscopy or sigmoidoscopy. In these, a flexible video camera is passed into the bowel through the anus. Samples from possible bowel cancer can be removed for microscopic diagnosis.

Some bowel cancers can also be detected using non-invasive imaging techniques such as ‘virtual colonoscopy’ or a magnetic resonance imaging (MRI) scan to create a three-dimensional image of the bowel. These techniques can miss polyps or small cancers that may be detected by colonoscopy and are currently considered inferior to a colonoscopy.

There is as yet no blood test that can reliably detect bowel cancer. Developing such a test is a goal of our bowel cancer researchers

For further information about bowel cancer detection please visit Bowel Cancer Australia.

How is bowel cancer treated?

Earlier diagnosis and better treatments have seen a doubling in survival rates from bowel cancer in Australia over the past 40 years.

When bowel cancer is detected early, before it has spread outside the bowel, it can often be cured by using surgery to remove the section of the bowel that contains the cancer.

When the cancer has spread outside the bowel (metastatic bowel cancer), surgery is usually combined with other treatments to kill any remaining cancer cells. Chemotherapy is an important part of treatment for metastatic bowel cancer. Several different chemotherapy drugs are used to treat bowel cancer, either alone or in combinations of two or more drugs.

Recently, some ‘monoclonal antibody’ treatments have been shown to be effective for treating bowel cancer. These contain antibodies that bind to proteins that are helping the bowel cancer to grow. This blocks the proteins’ function, preventing cancer growth. Monoclonal antibody treatments are sometimes combined with chemotherapy to increase their effect.

Bowel cancer treatment is currently hindered by a poor understanding of which patients will respond to which treatments. Genetic testing of bowel cancers is starting to reveal certain gene changes that predict whether a patient will respond well to a certain type of treatment. In particular, this testing can indicate whether monoclonal antibody treatments will be effective.

For more detailed information about bowel cancer treatment, please visit Bowel Cancer Australia.

WEHI researchers are not able to provide specific medical advice specific to individuals. If you have bowel cancer and wish to find out more information about clinical trials, please visit Australian Cancer Trials or the Australian New Zealand Clinical Trials Registry, or consult your medical specialist.