What Is Colorectal Cancer?
Learn the basics about cancers of the colon and rectum.

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Picture of man What Is Colorectal Cancer?

Colorectal cancer refers to cancer that develops in the colon or rectum. Colon cancer and rectal cancer are often discussed together because they are very similar.

What are the colon and rectum?
The colon and rectum are part of the digestive system, also called the gastrointestinal (or GI) system. When you eat, the food travels down the esophagus into your stomach, which starts to dissolve and digest it. Then it moves into the small intestine (or small bowel), where it is further broken down and most of the nutrients are absorbed into the body.

Next the food passes into the colon (also called the large intestine or large bowel). The colon is a muscular tube about five feet long. It removes water and salt, turning what remains into solid waste. The waste is stored in the rectum, the last six inches of the colon, until it can be eliminated from the body as a bowel movement.

What happens in colorectal cancer?
Colorectal cancer usually starts as a polyp, a mushroom-shaped growth on the lining of the colon or rectum. Polyps are not cancer, but some types of polyps can turn into cancer.

Some people inherit a risk for colorectal cancer, but in most cases doctors don't know what causes it. Age is the greatest single risk factor. More than 90 percent of people diagnosed with colorectal cancer are older than 50.

Colorectal cancer usually grows slowly. It may take years for a polyp to become cancerous. Screening tests such as colonoscopy can be done to look for polyps and remove them before they turn into cancer.

If the doctor suspects a growth is cancer, it will be sent to a lab to determine if it is, and how far it may have spread. This is called the stage of the cancer. Treatment is based on the stage. Surgery is the most common treatment for colorectal cancer. Other options such as radiation and chemotherapy may also be needed, especially if the cancer has spread beyond the colon.

Facts about colorectal cancer

  • Colorectal cancer is the fourth most common cancer in the U.S. and the second most deadly (after lung cancer).
  • Most people don't have symptoms until colorectal cancer has spread, making it harder to treat.
  • Screening tests can help find colorectal cancer early, when it can often be more easily cured.
  • More and more people are surviving colorectal cancer, thanks to improved screening and treatment.
By Lila Havens, Staff Writer
Created on 08/24/1999
Updated on 02/17/2010
Sources:
  • National Cancer Institute. What you need to know about cancer of the colon and rectum: risk factors.
  • American Cancer Society. Detailed guide: colon and rectum cancer.
  • American Gastroenterological Association. Colorectal cancer basics.
  • Compton C, Hawk E, Grochow L, Lee F Jr, Ritter M, Niederhuber JE. Colon cancer: etiology of colorectal cancer. In: Abeloff MD, Armitage JO, Niederhuber JE, Kastan MB, et al., eds. Abeloff's Clinical Oncology. 4th edition. Philadelphia, PA: Elsevier Churchill Livingstone; 2008.
Copyright © OptumHealth.
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