Colorectal cancer occurs in the lining, known as the mucosa, of the large intestine, which is made up of the colon and rectum.
It is the most common form of malignancy in the developed world, accounting for 20,000 deaths in the UK and 60,000 deaths a year in the US. Although the incidence and death rate from this cancer has changed little in the past 40 years, there are indications of cases falling recently. Generally, a quarter of cases arise as emergencies with either intestinal obstruction or perforation.
Risk factors: Colon cancer affects almost equal proportions of men and women, most commonly between the ages of 60 and 80 years. Genetic and environmental are believed to be significant factors in its occurrence - of which diet is probably the most important. A high-meat, high-fat and low-fibre diet is thought to encourage the production and concentration of carcinogens. High-risk people are advised to undergo genetic testing for one of the familial genes and may be advised to undergo regular screening including colonoscopy and blood tests.
Symptoms: A change in bowel movements and blood mixed in faeces.
Prognosis: Early detection is critical. Over a five-year period, there is a 50 per cent survival rate. Some 80 per cent of patients undergo surgery with removal of part of the colon. But half have a recurrence of the cancer. Chemotherapy and radiotherapy are also used in treatment depending on the development stage of the cancer.