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Colon Cancer Screening

Colorectal cancer screening can detect cancer; polyps; nonpolypoid lesions, which are flat or slightly depressed areas of abnormal cell growth; and other conditions. Nonpolypoid lesions occur less often than polyps, but they can also develop into colorectal cancer (12).

If colorectal cancer screening reveals a problem, diagnosis and treatment can occur promptly. In addition, finding and removing polyps or other areas of abnormal cell growth may be one of the most effective ways to prevent colorectal cancer development. Also, colorectal cancer is generally more treatable when it is found early, before it has had a chance to spread. We offer colon cancer screening for residents of Hurst, Euless, Bedford and the surrounding communities of Southlake, Grapevine, and Colleyville.

 What methods are used to screen people for colorectal cancer?

Health care providers may suggest one or more of the following tests for colorectal cancer screening:

Fecal occult blood test (FOBT)

This test checks for hidden blood in fecal material (stool). Currently, two types of FOBT are available. One type, called guaiac FOBT, uses the chemical guaiac to detect heme in samples of stool. Heme is the iron-containing component of the blood protein hemoglobin. Usually, samples of stool from three different bowel movements are collected for guaiac FOBT. The other type of FOBT, called immunochemical (or immunohistochemical) FOBT, uses antibodies to detect human hemoglobin protein in samples of stool (13–15). Depending on the type of immunochemical FOBT, stool samples from one to three bowel movements are collected. Studies have shown that FOBT, when performed every 1 to 2 years in people ages 50 to 80, can help reduce the number of deaths due to colorectal cancer by 15 to 33 percent (13–15).

Sigmoidoscopy—In this test, the rectum and lower colon are examined using a lighted instrument called a sigmoidoscope. During sigmoidoscopy, precancerous and cancerous growths in the rectum and lower colon can be found and either removed or biopsied. Studies suggest that regular screening with sigmoidoscopy after age 50 can help reduce the number of deaths from colorectal cancer (14). A thorough cleansing of the lower colon is necessary for this test.

Colonoscopy—In this test, the rectum and entire colon are examined using a lighted instrument called a colonoscope. During colonoscopy, precancerous and cancerous growths throughout the colon can be found and either removed or biopsied, including growths in the upper part of the colon, where they would be missed by sigmoidoscopy. However, it is not yet known for certain whether colonoscopy can help reduce the number of deaths from colorectal cancer. A thorough cleansing of the colon is necessary before this test, and most patients receive some form of sedation.

Virtual colonoscopy (also called computerized tomographic colonography)—In this test, special x-ray equipment is used to produce pictures of the colon and rectum. A computer then assembles these pictures into detailed images that can show polyps and other abnormalities. Because it is less invasive than standard colonoscopy and sedation is not needed, virtual colonoscopy may cause less discomfort and take less time to perform. As with standard colonoscopy, a thorough cleansing of the colon is necessary before this test. Whether virtual colonoscopy can reduce the number of deaths from colorectal cancer is not yet known.

Double contrast barium enema (DCBE)—In this test, a series of x-rays of the entire colon and rectum are taken after the patient is given an enema with a barium solution and air is introduced into the colon. The barium and air help to outline the colon and rectum on the x-rays. Research shows that DCBE may miss small polyps. It detects about 30 to 50 percent of the cancers that can be found with standard colonoscopy (14).

In addition, doctors often perform a digital rectal exam (DRE) during routine physical examinations and may use this test to check for abnormal areas in the lower part of the rectum. They may also perform a single-specimen guaiac FOBT on stool collected during a DRE, but research has shown that this approach is not very accurate and cannot be recommended as the only method of screening for colorectal cancer (16).

Scientists are still studying colorectal cancer screening methods, both alone and in combination, to determine how effective they are. Studies are also under way to clarify the potential risks, or harms, of each screening test. Question 5 includes a table outlining some of the advantages and disadvantages, including potential harms, of specific colorectal cancer screening tests.

 How can people and their health care providers decide which colorectal cancer screening test(s) to use and how often to be screened?

Several major organizations, including the U.S. Preventive Services Task Force (a group of experts convened by the U.S. Public Health Service), the American Cancer Society, and professional societies, have developed guidelines for colorectal cancer screening. Although some details of their recommendations vary regarding which screening tests to use and how often to be screened, all of these organizations support screening for colorectal cancer.

People should talk with their health care provider about when to begin screening for colorectal cancer, what tests to have, the benefits and harms of each test, and how often to schedule appointments.

The decision to have a certain test will take into account several factors, including the following:

The person’s age, medical history, family history, and general health

The accuracy of the test

The potential harms of the test

The preparation required for the test

Whether sedation is necessary during the test

The follow-up care after the test

The convenience of the test

The cost of the test and the availability of insurance coverage

The following list outlines some of the advantages and disadvantages, including potential harms, of the colorectal cancer screening tests described in this fact sheet.