NEW YORKTo increase colorectal cancer screening, the American Cancer Society (ACS) is encouraging the use of at least one of the four recommended screening tests. Previously, for persons of average risk, annual fecal occult blood test (FOBT) and flexible sigmoidoscopy every 5 years were only recommended in combination.
The updated guidelines state that annual FOBT plus flexible sigmoidoscopy every 5 years is preferred over either test alone, but the rationale for the new option is that any test alone is far better than not being screened at all, Robert A. Smith, PhD, the ACS’s director of Cancer Screening, said at a Cancer Research Foundation of America (CRFA) press briefing on colorectal cancer.
Extensive research by the ACS, Dr. Smith said, "made clear that the nation at this point in time is not prepared to fulfill a . . . requirement of annual FOBT and flexible sigmoidoscopy every 5 years." If primary care providers are "not prepared to offer the full range of options, we strongly encourage them to just do something," he said.
Alternative but more complex screening options for the average-risk individual, starting at age 50, are double-contrast barium enema every 5 years or colonoscopy every 10 years, he said.
Dr. Smith called annual FOBT "a very effective screening test." Although it is not the most effective screening test, "we could reduce colorectal cancer mortality by 30% or more if people would just do this one simple test every year," he said.
Doing the FOBT in a physician’s office with a single stool sample is not recommended, Dr. Smith stressed. Instead, samples from three consecutive bowel movements should be applied to a card that is then forwarded to a physician or laboratory for processing.
"Because cancers tend to bleed intermittently," he explained, "it’s very important to collect the full three samples." A test based on a single sample after a digital rectal examination, he noted, has limited sensitivity and will detect only half the cancers present in patients.
He noted that unlike most false-positive screening tests, a false-positive FOBT "offers something back." When a patient is referred to colonoscopy because of a positive FOBT and the colonoscopy does not reveal any important lesions, he said, "that person does not require any further colon screening for another decade."
Recent studies suggest that more than 80% of the important lesions throughout the colon could be picked up simply by doing flexible sigmoidoscopy, he said. The reach of a flexible sigmoidoscopy is about halfway into the colon under the best of circumstances, he noted, but if significant lesions are detected in the distal colon, they are likely to be present throughout the colon, and thus a colonoscopy should be performed.
Dr. Smith called colonoscopy "the Cadillac" of colorectal cancer screening tests. "It provides the opportunity to detect not only cancers but also adenomatous polyps and to remove them for biopsy all at the same examination." The recommended 10-year interval for colonoscopy in average-risk individuals, he noted, is based on the estimated 10-year "dwell time" for a polyp of less than 1 cm to become cancerous.
For people at increased or high risk of colorectal cancer, colonoscopy remains the recommended screening examination, starting at an earlier age and at different intervals, depending on the person’s risk factors.
If double-contrast barium enema is used, the guidelines now recommend that it be performed every 5 years instead of every 5 to 10 years. "We reduced the interval for the barium enema because of new data showing that it is somewhat less sensitive than previously thought," he said. Barium enema may be good for patients who cannot tolerate or have an aversion to endoscopy. For the full recommendations, see www.cancer.org.