The colon is the last portion of the digestive system in most vertebrates; it extracts water and salt from solid wastes before they are eliminated from the body. The last 13 inches of the colon is called the rectum.  Cancer that starts in the colon is called colon cancer. Cancer that starts in the rectum is called rectal cancer. Cancer of the colon and rectum is also called colorectal cancer.
Globally, cancer of the colon and rectum is the third leading cause of cancer in males and the fourth leading cause of cancer in females. It is the second-leading cancer in the United States.

The frequency of colorectal cancer varies around the world. It is common in the Western world and is rare in Asia and Africa.  Globally, the incidence of colorectal cancer is increasing in countries where the people have adopted western diets.