Colon cancer forms in the tissues of the colon, which is the largest part of the intestine. Rectal cancer forms in the tissues of the rectum, which is the last several inches of the large intestine before the anus. Either of these cancers is called colorectal cancer. 

In the United States, colorectal cancer is the fourth most common cancer in men after skin, prostate and lung and the fourth most common in women after skin, breast and lung. Yet it is the second leading cause of death from cancer.

According to the National Cancer Institute, in 2008, an estimated 108,070 new cases of colon cancer and 40,740 new cases of rectal cancer will occur. Nearly 50,000 people are expected to die of colon and rectal cancer in 2008.