Screening for Colorectal Cancer: Recommendations from the United States Preventive Services Task Force

What is the United States Preventive Services Task Force?

The United States Preventive Services Task Force (USPSTF) is a group of physicians and health care experts that reviews published research and makes recommendations about preventive health care.

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

Colorectal cancer is one of the most common types of cancer. Screening prevents colorectal cancer deaths by 1) finding and removing noncancerous outgrowths of the colon or rectum [polyps] before they become cancer and 2) finding cancer at early, curable stages. Available screening tests include fecal occult blood testing (FOBT), sigmoidoscopy, colonoscopy, and barium enema. Fecal occult blood testing uses a chemical reaction to find traces of blood in stool. Polyps and cancer can cause blood to leak into the stool, so a positive result on FOBT suggests the need for further testing. Sigmoidoscopy involves looking into the rectum and lower colon through a flexible tube-shaped instrument; colonoscopy uses a similar but longer instrument to look at the entire length of the colon. Doctors can take samples of the colon (biopsies) and remove polyps during both procedures. Barium enema involves taking x-rays of the abdomen after putting barium (a material that appears white on x-ray) into a person's colon by enema. If x-rays indicate a lesion in the colon, follow-up testing with colonoscopy is needed. Fecal occult blood testing is inexpensive, colonoscopy is expensive, and sigmoidoscopy and barium enema are moderately priced.

How did the USPSTF develop these recommendations?

The USPSTF reviewed published research to evaluate the benefits, harms, and costs of screening for colorectal cancer.

What did the authors find?

Several high-quality studies show that FOBT helps to decrease colorectal cancer deaths by up to one third among adults over age 50. Studies showing the effectiveness of sigmoidoscopy and colonoscopy are of lower quality but also show benefits. Barium enema can also detect polyps and cancer, but the effect of barium enema on deaths from colorectal cancer is unknown. Existing studies are unable to tell us which test is best. The seven studies of the cost-effectiveness of colorectal cancer screening found all tests to be cost-effective but could not identify a single best strategy or determine the best age to start and stop screening.

What does the USPSTF suggest that patients do?

The USPSTF strongly recommends that adults begin screening for colorectal cancer at age 50, the age at which risk starts to increase in the general population. The best options for screening include FOBT, sigmoidoscopy (alone or with FOBT), or colonoscopy. Barium enema is also an option, but it is less accurate than colonoscopy and its effects on colorectal cancer deaths are unknown. The Task Force did not recommend a specific screening test.

Patients should discuss the advantages and disadvantages of the various colorectal cancer screening tests with their doctors to decide which test is best for them. The frequency of screening depends on the test a patient uses: every 1 to 2 years for FOBT, every 5 years for sigmoidoscopy and barium enema, and every 10 years for colonoscopy.

What are the cautions related to these recommendations?

These recommendations do not apply to people who have a family history or a personal history that puts them at high risk for colorectal cancer. As better studies become available, the USPSTF may modify these recommendations.