What is colorectal cancer, or cancer of the colon or rectum?

Colorectal cancer is cancer of the colon or rectum. The colon and the rectum are part of the body's digestive system, which removes nutrients from food and stores waste until it passes out of the body. The colon and rectum form an almost 7 foot long muscular tube called the large intestine (also called the large bowel).

Most types of colorectal cancer begin with polyps (or grape-like growths on the lining of the colon and rectum). Polyps are very common in people over age 50 and usually are benign (not cancerous). But some polyps do develop slowly over the years into cancer, often causing no symptoms. Screening tests can find polyps that can be removed, preventing cancer. Screening tests can also pick up colorectal cancer at an early stage, when it can be cured.