Colorectal cancer, also known as bowel cancer, colon cancer, or rectal cancer, is any cancer that affects the colon and the rectum.Colon cancer typically affects older adults, though it can happen at any age. It usually begins as small, noncancerous  clumps of cells called polyps that form on the inside of the colon. Over time some of these polyps can become colon cancers.If colon cancer develops, many treatments are available to help control it, including surgery, radiation therapy and drug treatments, such as chemotherapy, targeted therapy and immunotherapy.