If you're approaching your 50th birthday, it's time to ask your doctor about colon and rectal cancer screening. Screening means being tested for a disease even though you don't have any symptoms.
Why get tested for a disease you may not have and may never get? Here are some good reasons:
- Colon cancer is the third most common type of cancer in the United States and the second leading cause of cancer deaths. Screening saves lives.
- Most colon cancer starts as polyps, mushroom-shaped growths on the lining of the colon and rectum. Screening can find and remove polyps before they become cancer.
- You can have colon cancer and not know it. It often doesn't cause any symptoms until it has grown large or spread to other parts of the body.
- Aging raises your risk for colon cancer. More than 90 percent of people who get colon cancer are over age 50, and the risk rises sharply after 50.
What tests are used for screening?
The U.S. Preventive Services Task Force (USPSTF) is the leading independent panel of experts in prevention and primary care. Its guidelines are considered the "gold standard" among doctors.
Screening tests recommended by the USPSTF are:
- Fecal occult blood test (FOBT). This is a simple, inexpensive test. It can detect tiny amounts of blood in your stool, which can be caused by colon cancer. This is not a very exact test because other things can also cause blood in the stool. If blood is found, a colonoscopy is usually needed to look for the cause.
- Sigmoidoscopy. During a sigmoidoscopy, a 2-foot-long lighted tube is inserted into the lower third of the colon. The test is usually done without anesthesia. If polyps or cancerous lesions are found, colonoscopy is needed to examine the rest of the colon.
- Colonoscopy. This procedure is the most expensive and most invasive, but it's also the most accurate. The scope is a thin, lighted tube that's connected to a video display monitor. This lets the doctor see inside all 5 feet of your large intestine and rectum while you are sedated. If polyps are found, they can be removed or biopsied during the same procedure.
The USPSTF did not find enough evidence to assess the benefits and risks of virtual colonoscopy or the stool DNA test. They said more research about the pros and cons of these tests is needed.
- Virtual colonoscopy (CT colonography). This is an advanced type of CT scan that creates 2-dimensional pictures and a 3-dimensional view of the inside of the colon and rectum. This test may be useful for some people who can't have or don't want to have more invasive tests.
- Stool DNA test. Cells from colon cancer or polyps often have DNA changes (mutations). This test looks for these mutations in cancer or polyp cells that are shed in the stool.
How often should I be screened?
Starting at age 50, men and women at average risk should choose one of these three screening options:
- A fecal occult blood test (FOBT) every year, or
- Flexible sigmoidoscopy every 5 years along with FOBT every 3 years, or
- Colonoscopy every 10 years
Other options for screening include:
- Virtual colonoscopy every 5 years
- Double contrast barium enema every 5 years
The USPSTF recommends screening be continued from age 50 to age 75. If you're older than 75, discuss the need for screening with your doctor. The USPSTF does not recommend colon cancer screening for people older than 85.
You may need to start screening at a younger age or be tested more often if:
- You or someone in your family has had colorectal cancer or colon polyps
- You have ulcerative colitis or Crohn's disease
- You have an inherited colon disorder such as familial adenomatous polyposis (FAP)
Created on 04/06/2000
Updated on 06/16/2011
- Levin B, Lieberman DA, McFarland B, et al. Screening and surveillance for the early detection of colorectal cancer and adenomatous polyps, 2008: a joint guideline from the American Cancer Society, the U.S. Multi-Society Task Force on Colorectal Cancer and the American College of Radiology. CA: A Cancer Journal for Clinicians. 2008;58;130-160.
- American Cancer Society. Colorectal cancer: early detection.
- U.S. Preventive Services Task Force. Screening for colorectal cancer: recommendation statement.