The third most common cancer diagnosed in adult Americans of both sexes, colorectal cancer (cancer of the colon or rectum) will affect more than 55,000 people in the U.S. this year.

Colorectal cancer usually begins as a tissue growth known as a polyp, which develops and becomes malignant over several years. Having a certain kind of these polyps, called adenomatous polyps, also known as adenomas, increases a person's risk of developing cancer, especially if there are many polyps or they are large.

Benefits of Colorectal Cancer Screening

Non-cancerous polyps that develop in the colon can be found through colorectal cancer screening and removed before they become cancerous. Colorectal screening also offers the best opportunity to detect colorectal cancer at an early stage, when treatment is more likely to be successful. When colorectal cancer is diagnosed before it has spread to nearby organs or lymph nodes, the five-year survival rate is 90 percent.

Colorectal Cancer Screening Tests

Fecal occult blood test (FOBT): The test uses a series of stool samples gathered by the patient to find occult (hidden) blood in feces, which can be a symptom of colorectal polyps, adenomas, or cancers.

Fecal immunochemical test (FIT) is a newer kind of stool blood test kit that detects a specific portion of a human blood protein. This test is done essentially the same way as conventional FOBT but is more specific and reduces the number of false positive results.

Sigmoidoscopy: A sigmoidoscope is a slender, flexible, lighted tube inserted through the rectum into the lower part of the colon. It may be connected to a video camera and video display monitor for a better view of the colon; however, because the tube is only about two feet long, it only shows less than half of the colon.

Colonoscopy: A colonoscope is a long version of a sigmoidoscope. It is inserted through the rectum into the colon and allows the doctor to see the lining of the entire colon. The colonoscope is also connected to a video camera and video display monitor so the doctor can closely examine the inside of the colon. If a polyp is found, the doctor will remove and examine it.

Barium enema with air contrast: This procedure, in which a chalky substance is used to open up the colon so it can be more accurately depicted in x-rays, is also called a double contrast barium enema.

Recommended Screening Schedule for Colorectal

Beginning at age 50, both men and women at average risk for developing colorectal cancer should follow the screening schedule below:

• FOBT or FIT every year plus flexible sigmoidoscopy every five years (preferred by the American
• Colonoscopy every 10 years

Before performing a sigmoidoscopy or coloscopy, your doctor should do a DRE (digital rectal examination) to detect any masses in the anal canal or lower rectum. But by itself, it is not a very sensitive test for detecting colorectal cancer due to its limited reach.

Should any of the other tests detect anything abnormal, they should be followed up with a colonoscopy.