Rectal cancer is similar to colon cancer in the types of cells involved in cancer growth, risk factors, staging and treatment. (Colon cancer is discussed in a separate section.) The death rates for colon and rectal cancers have been steadily declining for the past 20 years, due in part to fewer cases, earlier detection and advances in treatment.

The Rectum and Digestive System
The rectum is the lowest portion of the digestive system. This system, also called the gastrointestinal tract, is responsible for the processing of food into energy and the removal of waste.

Food travels from the mouth through the esophagus to the stomach, where it is partially broken down and sent to the small intestine. In the small intestine, food is further broken down and nutrients are absorbed. The small intestine feeds into the colon, where nutrients and water are absorbed and wastes are stored. Waste products are then pushed through to the rectum and pass out of the body through the anus.

Types of Rectal Cancer
Before cancer develops, polyps--small noncancerous growths of tissue--often appear in the rectum. There are two types of polyps: neoplastic and non-neoplastic. Non-neoplastic polyps have no cancerous potential. Neoplastic polyps can become cancerous. They are classified as tubular, tubulovillus or villous adenomas. Polyps are generally removed, and early removal may prevent them from developing into cancer.