Colorectal Cancer Screening

Colorectal cancer (cancer of the colon or rectum) is the second leading cause of cancer deaths in the United States. It is estimated that in 2006, about 145,000 new cases will be diagnosed and about 56,000 people will die of this disease. Among men, colorectal cancer is the third most commonly occurring cancer (after lung and prostate cancer) and among women it ranks third (after lung and breast cancer).

Who Is at Risk for Colorectal Cancer?
Most cases of colorectal cancer are diagnosed in individuals past the age of 50, with the average age of diagnosis being 70 for men and 73 for women. Age is considered a significant risk factor for developing this disease. Therefore, the American Cancer Society recommends routine screening for colorectal cancer for everyone over 50 years of age (see table for screening guidelines).

Regardless of age, there are certain people that are more likely to develop colorectal cancer. For example, certain hereditary colon conditions and certain types of non-cancerous colon disease can increase the risk of colorectal cancer. Having a relative with colorectal cancer also increases the risk. The screening guidelines for individuals at increased risk are somewhat different than for those over 50 years old who are at average risk (that is, without one of these identifiable risk factors).

How do you screen for colorectal cancer?
The goal of screening for colorectal cancer is to find the cancer at an early stage when it is more likely to be cured. It is believed that most colorectal cancers originate as growths of the intestinal lining of the colon or rectum, called polyps. Polyps usually have a slender stem with a tuft of tissue at the end of the stem. If a cancer can be prevented by finding and removing polyps that might eventually become cancerous, then this would fit the criteria for an ideal screening method. But how can a polyp be found? It is known that blood vessels around polyps are somewhat fragile and easily damaged by the passage of stool. The damaged vessels can release a small amount of blood into the stool. There is a test called the fecal occult blood test (FOBT), sometimes referred to as a “stool test,” which attempts to detect occult (hidden) blood present in the stool. A small amount of stool is obtained and smeared onto a special type of paper card. A few drops of a special chemical liquid are added to the card and if there is blood in the stool, the card will turn into a particular color. WHPP participants can get this type of colorectal cancer screening test as part of their free physical exam.

There are other screening options recommended by the American Cancer Society, including sigmoidoscopy and colonoscopy. A sigmoidoscopy is performed with a sigmoidoscope,which is a slender, flexible, hollow, lit tube about the thickness of a finger. It is inserted through the rectum to view the rectum and colon. The sigmoidoscope is about two feet long and can view only a portion of the colon (the colon is about five feet long). A colonoscopy is performed with a colonoscope (a longer version of the sigmoidoscope), which allows for viewing of the entire colon. These screening tests can be uncomfortable and involve somewhat greater risks than a “stool test.”

What if the stool test is abnormal?
The stool test cannot tell whether blood is from the colon or from other parts of the digestive tract. If this test is positive for the presence of blood, additional testing such as a colonoscopy is usually needed to determine the source of the blood. If polyps or other abnormalities are found (such as a tumor), they are removed and then sent to a lab to be tested to see if they are cancerous.