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Types of Cancer > Gastrointestinal Cancers > Colorectal Cancer > Overview
Colon Cancer: The Basics
Carolyn Vachani, RN, MSN, AOCN
Affiliation:
The Abramson Cancer Center of the University of Pennsylvania
Last Modified: March 1, 2008
What is the colon?
The colon is the longest portion of the large intestine, also known as the large bowel. The large intestine is the last part of the digestive tract. It is a tube that is about 5 to 6 feet in length; the first 5 feet make up the colon, which then connects to about 6 inches of rectum, and finally ends with the anus. By the time food reaches the colon (about 3 to 8 hours after eating), the nutrients have been absorbed and the remainder is liquid waste product. The colon's function is to change this liquid waste into solid stool. The stool can spend anywhere from 10 hours to several days in the colon before being expelled through the anus. It has been suggested that the longer stool remains in the colon, the higher the risk for colon cancer, but this has not been proven.
What is colon cancer?
Colon cancer is malignant tissue that grows in the wall of the colon. The majority of tumors begin when normal tissue in the colon wall forms an adenomatous polyp, or pre-cancerous growth projecting from the colon wall. As this polyp grows larger, the tumor is formed. This process can take many years, which allows time for early detection with screening tests.
Am I at Risk for Colon Cancer?
Colon cancer is the third most common type of cancer, in both males and females, in the Western world. The incidence is highest in African Americans, who are also more likely to die of the disease. Certain factors put people at higher risk, but with about 108,000 new cases each year in the United States, we must all be aware of this deadly disease. The risk of colon cancer rises substantially after age 50, but every year there are numerous cases reported in younger people. Individuals with a personal or family history of colon cancer, polyps, or inherited colon cancer syndromes (i.e., FAP and HNPCC), as well as patients with ulcerative colitis or Crohn's disease, are all at higher risk and may require screening at an earlier age than the general population. A person with one first degree relative (parent, sibling or child) with colon cancer is 2 to 3 times as likely to develop the cancer as someone who does not have an affected relative.
However, this does not mean that people without a family history are not at risk. In fact, about 80% of new colon cancer cases are diagnosed in people who would not be identified as "high risk". Studies of colon cancer cases found that lifestyle factors may put a person at higher risk. These factors include: a diet high in fat and red meat but low in fruits and vegetables, high caloric intake, low levels of physical activity, and obesity. In addition, smoking and excessive alcohol intake may play a role in colon cancer development. Despite avoiding all of these factors, some people will still develop colon cancer. With screening and early detection, these patients can be effectively treated in a majority of the cases.