Colorectal (or bowel) cancer is very common condition in Australia, affecting approximately 5% of people during their lifetime. It is more common with advancing age and is rare in young people. Men are slightly more likely to get bowel cancer than women. The exact cause of bowel cancer is unknown, however genetic and lifestyle factors both have a role. People with a family history of colorectal cancer are at increased risk of developing the condition, particularly if multiple relatives are affected or if cancer developed at a young age. Dietary factors have been extensively studied and it is likely that a diet low in fruit, vegetable and fibre and high in energy and red meat is associated with an increased risk of bowel cancer. It is also more common in those with obesity and a sedentary lifestyle. The lower bowel (rectum and sigmoid colon) is the most common site for cancer to develop, followed by the first part of the large bowel (caecum and ascending colon).
Common symptoms of colorectal cancer include a change in bowel habit or rectal bleeding. Other possible symptoms include abdominal pain, fatigue (due to anaemia from occult bleeding), weight loss or an abdominal swelling. Any symptoms suggestive of bowel cancer should be investigated, usually with colonoscopy.
Individuals with no symptoms and no family history or other risk factors for colorectal cancer are advised to commence screening at the age of 50 with faecal occult blood testing.
All colorectal cancers begin as polyps so removal of precancerous or very early stage cancerous polyps at colonoscopy is effective in reducing the risk of invasive bowel cancer. Most colorectal cancers require surgical treatment.