Colorectal cancer is the term used to describe cancer of the colon and/or rectum. The two cancers are grouped together because they share many common characteristics. Together, the colon and rectum make up the large intestine, a question mark-shaped bowel four feet in length. Colon cancer develops in all but the last few inches of the large intestine, between the appendix and rectum. Rectal cancer develops in the rectum, the last few inches of the large intestine that attaches to the anus. Colon cancer is more common. An estimated 95,000 new cases of colon cancer are diagnosed each year, compared to 39,000 cases of rectal cancer, according to the American Cancer Society.