Colorectal cancer is the second most common cause of cancer-related death in the United States. But the U.S. National Cancer Institute estimates that up to 90% of deaths from cancers of the colon and rectum could be prevented by routine screening.
For people at average risk, The University of Texas MD Anderson Cancer Center recommends that screening for colorectal cancer start at age 50 years.
Types of screening
Most colorectal screening tests examine the colon and rectum for tissue growths called polyps. Polyps usually are not harmful, but some can gradually develop into cancer. Screening can identify potentially dangerous polyps before cancer develops or spreads.
Colorectal cancer screening commonly involves one of the following tests.
Colonoscopy. This thorough examination uses a flexible instrument tipped with a lighted video camera to inspect the rectum and entire colon for abnormalities. During the exam, doctors can use the instrument to remove polyps or take tissue samples for examination. Most people receive sedation before this exam, as the procedure causes some discomfort. For people age 50 years or older at average risk of colorectal cancer, colonoscopies should be performed every 10 years.
Virtual colonoscopy. MD Anderson offers this less-invasive alternative to a traditional colonoscopy. Using computed tomography, doctors produce pictures of the colon and rectum. No sedation is needed. If the images reveal any polyps or other abnormalities, a traditional colonoscopy will be needed to remove them. Generally, a virtual colonoscopy should be done every 5 years. Check with your insurance provider about whether this new test is covered under your medical plan.
Sigmoidoscopy. This test is similar to a colonoscopy and allows doctors to see and remove suspicious polyps, but a sigmoidoscopy examines only the rectum and lower part of the colon (the descending colon and the sigmoid colon). A sigmoidoscopy is less invasive than a colonoscopy but cannot see polyps on the other side of the colon. A sigmoidoscopy should be repeated every 5 years.
Double-contrast barium enema. This test views the lining of the rectum and colon for abnormalities. In this procedure, the colon is filled with radiographic contrast material by an enema, air is added to expand the colon, and then a series of x-ray scans are performed. As in a virtual colonoscopy, if any polyps are found, a colonoscopy will be needed to remove them. This screening should generally be repeated every 5 years.
Stool tests. Three take-home stool tests for colorectal cancer screening have been approved by the U.S. Food and Drug Administration. Two of these, the fecal immunohistochemical test (FIT) and the fecal occult blood test (FOBT), test for substances that suggest blood in the stool sample. The other, the DNA stool test, detects altered DNA in stool. Blood or altered DNA may be a sign of colorectal cancer, but a full colonoscopy will be needed to confirm the presence of cancer. Because stool tests may not be able to identify precancerous abnormalities that could be removed to prevent colon cancer, MD Anderson prefers colonoscopy or virtual colonoscopy. If a stool test is used, the FIT or FOBT should be repeated every year or the DNA test every 3 years.
For colonoscopy, virtual colonoscopy, sigmoidoscopy, and double-contrast barium enema, people usually must prepare the day before the test by consuming only clear liquids and by using laxatives or enemas.
Your doctor can help you compare benefits of each screening test with the risks involved and develop a strategy that is right for you. In addition to regular screening, MD Anderson recommends that you pay attention to signs that something might be wrong, like bleeding or a change in your bowel movements, and report these signs to your doctor immediately.
What is your risk?
You and your doctor can discuss your personal and family history to customize your screening routine. If you are at average risk of colorectal cancer, MD Anderson recommends you begin regular screening at age 50 years and continue through age 75 years.
People with an increased risk of colorectal cancer are advised to begin screening at a younger age and/or repeat tests more frequently, depending on the reason for the increased risk. You may have an increased risk of colorectal cancer if you have an inflammatory bowel disease such as chronic ulcerative colitis or Crohn disease or if you or a family member had or have colorectal cancer, precancerous colon polyps (adenomas), or a hereditary cancer syndrome such as familial adenomatous polyposis or hereditary nonpolyposis colorectal cancer (Lynch syndrome).
Regular screening and staying aware of your body can help detect colorectal cancer early, when it may be more easily treated, or remove polyps before they can turn into cancer.
For more information, ask your physician, call askMDAnderson at 877-632-6789, or read MD Anderson’s colorectal cancer screening guidelines.
OncoLog, March 2016, Volume 61, Issue 3