Bowel, or colorectal cancer, occurs in the colon (large intestine) or back passage (rectum). About 80% of bowel cancers occur in the large intestine and 20% in the rectum. Anal cancer (cancer of the anus) is rare.
Our body is made up of more than 37 trillion cells that change and grow naturally. Cancer starts when cell changes go wrong and cells begin to divide in an uncontrolled way. Bowel cancer begins as a solid tumour, usually developing from small polyps that are found on the bowel wall. Many of us have these polyps, and as we age they are more common. Most will never turn into cancer, but over time they can.
Your doctor can remove polyps to stop them from turning into cancer. In common with many other cancers, bowel cancer is most worrying when it has spread (metastasised). At the beginning, it travels through the wall of the bowel, then into lymph nodes and finally to distant organs – most often the liver.
Who gets bowel cancer?
More than 42,000 people annually are diagnosed with bowel cancer and it is the 2nd most prevalent cancer that affects both men and women. 1 in 14 men (7%) and 1 in 19 women (5%) will be diagnosed with bowel cancer in their lifetime. Bowel cancer can affect people of any age, although 94% of bowel cancer is diagnosed in those over 50 and four out of ten people are diagnosed over the age of 75.