Task Force Recommends Screening for All Age 50 and Over

ROCKVILLE, Maryland—Every man and woman age 50 or older with an average risk of colorectal cancer should be screened for colorectal cancer periodically, according to a new and strong recommendation from the US Preventive Services Task Force (USPSTF). The panel’s report also said screening for the disease at an earlier age in people at high risk is a reasonable practice.

"The USPSTF found fair to good evidence that several screening methods are effective in reducing mortality from colorectal cancer," the report said. "The USPSTF concluded that the benefits from screening substantially outweigh potential harms, but the quality of evidence, magnitude of benefit, and potential harms vary with each method."

The panel is an independent group of experts sponsored by the Agency for Healthcare Research and Quality (AHRQ) that makes recommendations across the prevention spectrum. Its recommendations do not represent federal policy but are widely accepted within medicine. It made its new recommendations after reviewing an updated evaluation of the scientific literature pertaining to colorectal screening techniques.

"The USPSTF found good evidence that periodic fecal occult blood testing (FOBT) reduces mortality from colorec-tal cancer and fair evidence that sigmoidoscopy alone or in combination with FOBT reduces mortality," the report said.

Although the panel did not find direct evidence that colonoscopy reduced colorectal cancer mortality, its efficacy "is supported by its integral role in trials of FOBT, extrapolation from sigmoi-doscopy studies, limited case-control evidence, and the ability of colonoscopy to inspect the proximal colon."

Double-contrast barium enema offers an alternative to whole-bowel examination, but its sensitivity is below that of colonoscopy, and no direct evidence supports its efficacy in reducing mortality, the USPSTF concluded.

It also found insufficient evidence that newer screening techniques, such as computed tomographic colography (also known as virtual colonoscopy), improve the outcomes of patients with colorectal cancer. CT colography has proven relatively sensitive and specific in research settings—85% to 90%—but recent reports suggest a lower accuracy when performed by less experienced practitioners.

"There are insufficient data to determine which strategy is best in terms of the balance of benefits and potential harms or cost-effectiveness," the panel said. "Studies reviewed by USPSTF indicate that colorectal cancer screening is likely to be cost-effective (less than $30,000 per additional year of life gained) regardless of the strategy chosen."

In deciding which screening strategy to choose, physicians should consider a patient’s preference, medical contraindi-cations, patient adherence, and the resources available for testing and follow-up, the panel added.

Moreover, it found no direct evidence by which it could determine optimal intervals for screening tests save for FOBT, which reduces mortality more when used annually than every 2 years. Nor could the panel determine an age at which to recommend discontinuing screening for colorectal cancer.

Although FOBT and sigmoidoscopy combined may find more tumors and larger polyps than either technique used alone, the additional benefits and risks of doing the two screenings together remain uncertain, the USPSTF said. When both are used, FOBT should generally precede sigmoidoscopy because a positive FOBT indicates the need for colon-oscopy.

"There is little evidence to determine the effectiveness of either digital rectal examinations [DREs] or a single office FOBT using a stool sample obtained on DRE," the panel said.

Colonoscopy

Colonoscopy is a more sensitive and specific test for colorectal cancer and large polyps than other screening techniques, but it also carries higher risks, including a small danger of bleeding and perforation of the bowel, the panel said. "It is not certain whether the potential added benefits of colonoscopy relative to screening alternative are large enough to justify the added risks and inconvenience for all patients," the report stated.

The panel further noted that the accuracy of colonoscopy is difficult to evaluate because the procedure is usually considered the criterion standard, and its specificity is also difficult to define. "Many patients will have polyps detected or removed on colonoscopy, but only a minority of those would have developed cancer," the report stated.

Colonoscopy’s effectiveness in preventing colorectal cancer or mortality has never been tested in a randomized clinical trial. However, "the National Polyp Study, a randomized trial of different intervals of surveillance after polypectomy, estimated that 76% to 90% of cancers could be prevented by regular colono-scopic surveillance exams," the panel said. "A single case-control study suggests that colonoscopy is associated with a lower incidence of colon cancer and a lower mortality."

For more information on the report, go to http://www.preventiveservices.ahrq.gov.