Cancer that begins in the colon is called colon cancer, while cancer in the rectum is known as rectal cancer. Cancers that affect either of these organs may be called colorectal cancer. Though not true in all cases, the majority of colorectal cancers generally develop over time from adenomatous (precancerous) polyps. Polyps (growths) can change after a series of mutations (abnormalities) arise in their cellular DNA. Some of the risk factors for colorectal cancer involve a family history of colon or rectal cancer, diet, alcohol intake, smoking and inflammatory bowel disease.