Bowel cancer

Bowel cancer is the second most common cancer affecting people in Australia. It is estimated that about 15,000 people are diagnosed with bowel cancer every year.

About one in 21 men and one in 30 women will develop bowel cancer before the age of 75. It is most common in people over 50, but it can occur at any age.

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 eight years
• lifestyle factors – being overweight, having a diet high in red meat (particularly processed meats such as salami or ham), drinking alcohol and smoking
• strong family history – a small number of bowel cancers run in families
• 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 cancer may have an increased risk of bowel cancer
• rare genetic disorders – a small number of bowel cancers are associated with an inherited gene.

Some factors reduce your risk of developing bowel cancer.

These include being physically active, maintaining a healthy weight, cutting out processed meat, cutting down on red meat, reducing alcohol consumption and eating a high-fibre diet.

Sometimes bowel cancer runs 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. This is especially the case if they were diagnosed before the age of 55, or if there are two close relatives on the same side of your family with bowel cancer.

A family history of other cancers, such as endometrial cancer, may also increase your risk of developing bowel cancer.

There are also two rare genetic conditions that occur in some families. These cause a small number (5–6%) of bowel cancers.

Familial adenomatous polyposis (FAP) – This condition causes hundreds of polyps to form in the bowel. If polyps caused by FAP are not removed, they may become cancerous.

Lynch syndrome – Previously known as hereditary non-polyposis colorectal cancer (HNPCC), this syndrome is characterised by a fault in the gene that helps the cell’s DNA repair itself. Having Lynch syndrome increases the risk of developing bowel cancer and other cancers.

If you are concerned about your family risk factors, talk to your doctor about having regular check-ups or ask for a referral to a family cancer clinic. To find out more, call Cancer Council 13 11 20.