In a change from its previous recommendation, the U.S. Preventive Services Task Force now recommends that adults age 50 to 75 be screened for colorectal cancer using annual high-sensitivity fecal occult blood testing, sigmoidoscopy every five years with fecal occult testing between sigmoidoscopic exams, or colonoscopy every 10 years.

According to the task force, which is supported by the Agency for Healthcare Research and Quality (AHRQ; Rockville, Maryland), good evidence exists that using these methods save lives. The recommendation and the accompanying summary of evidence is posted in the Annals of Internal Medicine online at and will appear in the Nov. 4 print edition of the journal.

The task force recommends against routine colorectal cancer screening in adults between the ages of 76 and 85 because the benefits of regular screening were small compared with the risks. The task force also recommends that adults over the age of 85 not be screened at all because the harms of screening may be significant, and other conditions may be more likely to affect their health or well-being.

For people of all ages, the task force found insufficient evidence to assess the benefits and harms of computed tomographic (CT) colonography and fecal DNA testing as screening methods for the disease. Further, these task force recommendations don't apply to people with a personal history of certain types of polyps who are being monitored regularly for the condition or to those who have a family history of rare syndromes that increase a person's chances of getting colon cancer.

This recommendation strengthens the task force's previous position in 2002, when it recommended screening for colorectal cancer but noted that evidence was insufficient to recommend one screening method over another. This is also the first time that the task force has indicated an age that people should stop being screened for colorectal cancer.

Sigmoidoscopy is the minimally invasive medical examination of the large intestine from the rectum through the last part of the colon. There are two types of sigmoidoscopy: flexible sigmoidoscopy, which uses a flexible endoscope, and rigid sigmoidoscopy, which uses a rigid device.

Flexible sigmoidoscopy is generally the preferred procedure. Sigmoidoscopy is a very effective screening tool, similar to but not the same as colonoscopy. Sigmoidoscopy only examines up to the sigmoid, the most distal part of the colon, while colonoscopy examines the entire large bowel.

A fecal occult blood test finds blood in the stool by placing a small sample of stool on a chemically treated card, pad or wipe. Then a special chemical solution is put on top of the sample. If the card, pad or cloth turns blue, there is blood in the stool sample.

Although colonoscopy is considered to be the standard against which other screening tests are compared, the test is not perfect and may in fact miss some polyps and colorectal cancer. Because colonoscopy is an invasive procedure, it has greater risk of complications than any other screening methods.

Sigmoidoscopy or fecal occult blood testing are less invasive and have a lower risk of harms. However, patients who receive positive test results for detection of polyps will require a follow-up colonoscopy regardless of the screening test used. Because the risks and benefits of all tests vary, patients and clinicians are encouraged to decide together which test is appropriate.

"Screening for colorectal cancer saves lives," said Task Force Chair Ned Calonge, MD, who is chief medical officer for the Colorado Department of Public Health and Environment (Denver). "Current rates for colorectal cancer screening are much lower than other types of cancer screening. We hope patients and physicians will discuss the potential benefits and harms and choose an appropriate screening method for them."

Colorectal cancer is the third-most-common cancer and the second leading cause of cancer death in the U.S. Research funded by the AHRQ and the National Cancer Institute, featured in the September 2008 Medical Care Supplement, examined ways to improve the delivery of colorectal cancer screening in primary care. In 2005, only about half of adults age 50 and older had been screened for the disease.

The task force is the leading independent panel of experts in prevention and primary care. It says it conducts "rigorous, impartial assessments of the scientific evidence for the effectiveness of a broad range of clinical preventive services, including screening, counseling and preventive medications." Its recommendations are considered the gold standard for clinical preventive services.