One third of
colorectal cancer deaths could be prevented with regular screening, studies show. Because many people do not get screened, however, the disease is the third leading cause of cancer deaths in the United States. Cancer of the colon and rectum is both preventable and treatable if detected early.
Colorectal cancer can be prevented by looking for and removing polyps and lesions in the colon. Because these are found most often in people 50 years of age and older, experts recommend universal screening in this age group. Among the groups making this recommendation are the U.S. Preventive Services Task Force, the U.S. Centers for Disease Control and Prevention, the American Cancer Society, the American Academy of Family Physicians, and a multidisciplinary physician panel convened by the U.S. Agency for Healthcare Research and Quality (with the U.S. Multi-Society Task Force on Colorectal Cancer).
- Adults 50 years of age and older who are of average risk should be routinely screened for colorectal cancer.
- Earlier, more frequent, and the most rigorous screening is appropriate at a younger age for those who have risk factors, often beginning at age 40.
For those of African descent, the American College of Gastroenterology recommends starting testing at a younger age:
- Americans of African descent should get screened starting at 45 years of age. The “first line” screening test for this group is a colonoscopy, which should be repeated every 10 years, suggests the gastroenterology group, unless additional risk factors, such as family history, warrant more frequent testing.
The recommendation reflects findings that Americans of African descent tend not only to be diagnosed with this cancer at a younger age than others, but also to survive for a shorter period of time. Also, some evidence shows that those of African descent have more right-sided cancers and polyps (making the colonoscopy of greatest benefit).
- There is no defined age when it is recommended to stop screening.
Get tested periodically until your age or other illnesses limit your life expectancy. A 2003 study by the Cleveland Clinic Foundation concluded that colonoscopy screening is worthwhile into the eighth and ninth decades.
Which test should you have?
Recommendations on colon cancer screening name seven acceptable tests. The tests are really of two types: lab tests analyzing your stool samples and procedures in which a specialist views images of the inside of your colon.
- Lab tests find telltale blood or DNA—signs that cancer is present—in a stool sample. The three types of lab tests are the fecal occult blood test (FOBT), the immunochemical fecal occult blood test (iFOBT), and the stool DNA test.
- Imaging procedures show abnormalities—polyps and lesions—on the empty colon’s lining.
- Two of these use a scope with a video camera: colonoscopy views the entire length of the colon, and flexible sigmoidoscopy views the lower third. These two approaches to screening are also able to remove any polyps that are found and allow them to be tested for presence of cancer cells.
- The other two use x-rays: virtual colonoscopy—a computed tomography (CT) scan—combines many cross-sectional images into 2-D and 3-D views of the colon, and a double-contrast barium enema (DCBE) provides x-ray views of lumps, polyps, and abnormalities in the outline of the colon. However, these approaches only allow visualization of the polyps. To remove the polyps would require a follow-up colonoscopy or flexible sigmoidoscopy.
In 2008, guidelines from the American Cancer Society, American College of Radiology, and U.S. Multi-Society Task Force on Colorectal Cancer urged getting a screening test good at finding both cancer and polyps, provided a procedure of this type is available to you and an invasive test is acceptable to you. They recommend relying more on the tests that can help prevent cancer rather than tests that only detect it. Their guidelines also broke ground in approving two more tests for screening: DNA analysis of the stool sample and virtual colonoscopy.
No single test is preferred for all individuals. Any one of the recommended approaches described below can be appropriate for a person of average risk, depending on the circumstances. The first four can find both polyps and cancer:
Particularly when the ease and safety of a sample-based test is desirable, one of the three lab tests can be used:
- Fecal occult blood test (FOBT) or the simpler immunochemical fecal occult blood test (iFOBT or FIT) every year
- Stool DNA test—optimal frequency not yet known
Each test can be used alone, or two test types can be used in combination. When the findings are abnormal, a colonoscopy is needed.
Colonoscopy is the most accurate and thorough test, but also the most costly and invasive; it is especially appropriate for those with risk factors. You may have reasons to choose a simpler test. Stool sample and sigmoidoscopy tests are easier, but not as accurate; they are better used together and can be the best approach in specific situations. As the U.S. Centers for Disease Control and Prevention notes, any of the recommended tests is better than no test.
Research is showing that attention needs to be paid not only to polyps, but also to flat lesions on the colon’s lining. This may further influence the types of tests recommended. It also means the person viewing your images must work more carefully than ever.
Decision aids
Talk to your health care provider about the screening tests recommended for you. Some employers, health plans, and health care providers provide decision aids. Booklets, online tools, DVDs, and videos have been created on colon cancer screening tests.
Also, don’t neglect the protection of getting re-tested at the recommended interval. Ask or sign up for a mailed or e-mailed reminder (link below), or mark your calendar or date book.
Links
MedlinePlus: Colorectal Cancer
Healthwise, Inc. Decision Point: Which test should I have to screen for colorectal cancer?
To use a calculator to determine your risk,
click here.
To sign up for a personal colon cancer screening reminder,
click here.
Sources
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