Cancer occurs when cells within a certain part of the body divide and multiply too rapidly, producing a lump of tissue known as a tumour. In bowel cancer, this occurs in the colon or rectum.
Bowel cancer often starts as small, non-cancerous polyps that form on the walls of the large intestine (bowel). Over time, some of these polyps may become cancerous.
If the polyps do become cancerous, the cancer cells can spread to the lymph nodes and bloodstream to other parts of the body, most commonly the liver and the lungs.
Risk factors for bowel cancer
Scientists are still unsure what causes cancer to develop in the bowel, but certain factors make you more likely to develop it, including:
- Increasing age – in New Zealand 90% of people who develop bowel cancer are over the age of 50 years.
- Family history of bowel cancer – especially if you have a close family member who has been diagnosed with bowel cancer at a young age (under 55 years)
- Lifestyle factors, such as:
- a diet high in red and processed meat, and low in fruit and vegetable fibre
- smoking
- drinking large amounts of alcohol
- inactive lifestyle.
- Having an inflammatory bowel condition, such as ulcerative colitis, for more than 10 years.
- Having a rare inherited condition, known as polyposis that can lead to bowel cancer. Read more about polyposis(external link)(external link) from the NZ Familial GI Cancer Service.
