The colon, in four sections, makes up the majority of the 5-foot length of the large intestine. In the alimentary canal (the path that food follows through your body), the colon follows the small intestine and comes before the rectum. The colon is responsible for absorbing water, vitamins, and minerals from the intestinal contents and conserving them. It also mixes the intestinal contents, forms stools, and rids the body of undigested material.

Colon and rectum cancers are sometimes referred to together as “colorectal cancer” - in this article, they will be referred to as “colon cancer.” Together they are the third most common cancer in adults and the second leading cause of cancer deaths in men and women in the United States. Most cases of colon cancer begin with the development of benign polyps, finger-like growths that protrude into the intestinal cavity. These benign polyps are relatively common in people over age 50. They can become cancerous, though, with the ability to invade the normal colon and spread to other parts of the body (metastasize). The tumors can create blockages in the intestine, preventing elimination. As estimated by the American Cancer Society, about 50,000 Americans die from colon cancer each year, and approximately 149,000 new cases are diagnosed.

The exact causes of colon and rectal cancer are not known, but risk appears to be associated with genetic, dietary, and lifestyle factors. Those with a personal or family history of colon cancer or polyps are at a higher risk, as are those with ulcerative colitis, a form of inflammatory bowel disease, and immunodeficiency disorders. A rare inherited disease called familial adenomatosis or polyposis causes benign polyps to develop early in life and causes cancer in almost all affected persons unless the colon is removed. Risk also increases with age and with the occurrence of cancers in other parts of the body. High fat and meat diets are a risk factor, especially combined with minimal fruit, vegetable, and fiber intake. Lifestyle factors include cigarette smoking, obesity, and a sedentary lifestyle.