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Types of Cancer > Gastrointestinal Cancers > Colorectal Cancer > General Information
Rectal Cancer: The Basics
Carolyn Vachani, MSN, RN, AOCN
Affiliation:
The Abramson Cancer Center of the University of Pennsylvania
Last Modified: February 27, 2008
What is the rectum?
The rectum is located at the end of the colon and is about 5 inches in length. The rectum is normally empty, except when stool is propelled by the upper colon into the rectum just prior to a bowel movement. At that time, stool is ready to be excreted through the anal canal. The anal canal has two muscular "valves", called the internal and external sphincters, through which the stool must pass. The sphincters allow us to retain stool until we are ready to have a bowel movement, at which time the sphincters relax, releasing the stool.
What is rectal cancer?
Rectal cancer is malignant (or cancerous) tissue that grows in the wall of the rectum. The majority of tumors begin when normal tissue in the rectum wall forms an adenomatous polyp, or pre-cancerous growth, projecting from the rectal wall lining. As this polyp grows larger, the tumor is formed. This process can take many years, which allows time for early detection with screening tests.
Am I at risk for rectal cancer?
In 2008, there will be an estimated 40,740 new cases of rectal cancer in the United States (23,490 in men and 17,250 in women). In general, colon and rectal cancers are grouped together and have the same risk factors associated with them. The average age of diagnosis is 66 years of age, and risk increases with age. Individuals with a personal or family history of colorectal cancer or polyps, inherited colorectal cancer syndromes (i.e., FAP and HNPCC, and patients with ulcerative colitis or Crohn's disease are at higher risk, and thus may require screening at an earlier age than the general population. A person with one first degree relative (parent, sibling or child) with colon cancer is 2 to 3 times as likely to develop the cancer as someone who does not have an affected relative.
However, this does NOT mean that people without a family history are not at risk. About 80% of new colorectal cancer cases are diagnosed in people who would not be identified as "high risk". Studies of colorectal cancer cases found that lifestyle factors may put a person at higher risk. These factors include: a diet high in fat and red meat but low in fruits and vegetables, high caloric intake, low levels of physical activity, and obesity. In addition, smoking and excessive alcohol intake may play a role in colorectal cancer development.
Despite avoiding all of these factors, some people will still develop colon or rectal cancer. With screening and early detection, these patients can be cured in a majority of the cases.