Understanding bowel cancer - the basics

What is bowel cancer?

Inside your abdominal cavity is the long, tubular digestive tract. The second part of this tube -- the large intestine -- is composed of the colon, which stretches 120 cm to 180 cm (four to six feet), and the rectum, which is only 10 to 15 cm (four to six inches) long.

The inner lining of this "colorectal tube" can be a fertile breeding ground for small tumours, called polyps. By the age of 60, an estimated 30-40% of people will have at least one adenomatous polyp - that is, a polyp with potential to become malignant,- in their colon. Most bowel (or colorectal) cancers develop from polyps in the glandular tissue of the intestinal lining.

Most polyps are benign, but adenomatous polyps are known to be pre- cancerous. If bowel cancer is diagnosed and treated early, while the tumour is still localised, the disease is highly curable, with five-year survival rates of about 90%. If the tumour continues to grow, cancer can spread directly through the bowel wall to surrounding tissues and organs, as well as into the bloodstream or lymphatic system.

Once the cancer spreads to lymph nodes or other organs, successful treatment becomes more difficult. Depending on how advanced the disease is, five-year survival rates for bowel cancer range from around 6% to 93%.

Cancers of the colon and rectum are the third most common type of cancer in the UK. According to the NHS over 38,000 new cases of bowel cancer are diagnosed each year. In 2007, around 17,600 new cases of bowel cancer were diagnosed in women making it the second most common cancer in women after breast cancer, and around 21,000 cases were diagnosed in men making it the third most common cancer in men after prostate and lung cancer. Around two thirds of bowel cancers develop in the colon, and one third develop in the rectum.

Although diagnosis is often possible at an early stage, many people delay seeking medical care because they are embarrassed about, or fearful of, symptoms related to their bowels. The risk of bowel cancer increases significantly after the age of 50 and continues to increase with age.