Screening for Colorectal Cancer: U.S. Preventive Services Task Force Recommendation

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The full reports are titled "Screening for Colorectal Cancer: U.S. Preventive Services Task Force Recommendation Statement"; "Screening for Colorectal Cancer: A Targeted, Updated Systematic Review for the U.S. Preventive Services Task Force"; and "Evaluating Test Strategies for Colorectal Cancer Screening: A Decision Analysis for the U.S. Preventive Services Task Force." They are in the 4 November 2008 issue of Annals of Internal Medicine (volume 149). The first report was written by the U.S. Preventive Services Task Force; the second report was written by E.P. Whitlock, J.S. Lin, E. Liles, T.L. Beil, and R. Fu; and the third report was written by A.G. Zauber, I. Lansdorp-Vogelaar, A.B. Knudsen, J. Wilschut, M. van Ballegooijen, and K.M. Kuntz.

Who developed these guidelines?

The U.S. Preventive Services Task Force is a group of health experts that makes recommendations about preventive health care.

What is the problem and what is known about it so far?

Colorectal cancer (cancer of the colon [large intestine] or rectum) is a common cause of death from cancer in the United States. Screening helps patients by detecting abnormal growths in the colon (polyps) before they become cancer and by detecting cancer at an early, curable stage.

Common screening tests for colorectal cancer screening include fecal occult blood testing (FOBT), sigmoidoscopy, and colonoscopy. Fecal occult blood testing uses a chemical reaction to find traces of blood in stool. A positive result on FOBT should lead to colonoscopy. Sigmoidoscopy involves looking into the rectum and lower colon through a flexible tube-shaped instrument with a camera on its tip. Colonoscopy uses a similar but longer instrument to look at the entire colon. During colonoscopy, doctors can take samples of the colon (biopsies) and remove polyps.

Newer tests that may help to screen for colorectal cancer include computed tomography, colonography ("virtual colonoscopy"), and stool tests that use DNA-based technology. "Virtual colonoscopy" uses x-rays and computers to produce multiple thin-sliced images of the inside of the colon. It takes about 10 minutes and does not require sedation, but it requires that a patient take laxatives before the test, like regular colonoscopy, and also involves exposure to radiation. Abnormal results from virtual colonoscopy need to be followed up with regular colonoscopy. The DNA-based stool test is more expensive than FOBT but might be more accurate.

How did the U.S. Preventive Services Task Force develop these recommendations?

The U.S. Preventive Services Task Force reviewed published studies to learn about the risks and benefits of various colorectal cancer screening tests and of screening patients at different ages. They also used computer models to help define the risks and benefits of different starting and stopping ages for screening on the basis of the best evidence from the published studies.

What did the authors find?

Good-quality evidence shows that screening with FOBT, sigmoidoscopy, or colonoscopy reduces deaths from colorectal cancer for patients age 50 to 75 years. Evidence also shows that the relative benefit of colorectal cancer screening decreases after age 75 years because people become increasingly likely to die of another cause before they die of colorectal cancer. The USPSTF concluded that after age 85 years, the risks of screening outweigh the benefits.

What does the U.S. Preventive Services Task Force recommend that patients and doctors do?

Patients age 50 to 75 years should be screened for colorectal cancer with FOBT, sigmoidoscopy, or colonoscopy. Patients and doctors should discuss the advantages and disadvantages of the different tests when choosing which test to use.

Patients age 76 to 85 years should only consider continuing screening if they are likely to live for at least another 10 years.

Patients older than 85 years should not have colorectal cancer screening.

Patients who are considering virtual colonoscopy or DNA-based stool testing should understand that not enough information exists to know the definite role of these tests in colorectal cancer screening.

What are the cautions related to these recommendations?

The recommendations apply only to patients who are at average risk for colorectal cancer and do not have symptoms that could be due to colorectal cancer. The recommendations may change as new studies become available.