On June 15, the U.S Preventive Services Task Force (USPSTF) published its final recommendation statement(www.uspreventiveservicestaskforce.org) and evidence summary(www.uspreventiveservicestaskforce.org) on screening for colorectal cancer and found that "convincing evidence" supported screening adults ages 50-75 -- an "A" recommendation.(www.uspreventiveservicestaskforce.org)
The AAFP's Commission on Health of the Public and Science's Subcommittee on Clinical Preventive Services reviewed the USPSTF's recommendation and agreed that screening this age group for colorectal cancer should be recommended. However, in the AAFP's final recommendation statement, the subcommittee made this a "B" recommendation and also differed from the task force on suggestions for recommended screening tests.
In addition, the AAFP agreed with the USPSTF's recommendation that the decision to screen for colorectal cancer in adults ages 76-85 be an individualized one, taking into account the patient's overall health and previous screening history -- a "C" recommendation. The Academy also recommended against screening for colorectal cancer in adults older than age 85 -- a "D" recommendation.
AAFP Recommendation Explained
Jennifer Frost, M.D., medical director for the AAFP Health of the Public and Science Division, told AAFP News the biggest difference between the AAFP's recommendation statement and that of the USPSTF is that the Academy's statement offers more specific guidance to family physicians about what tests are supported by the evidence.
"The USPSTF addressed these differences in its Clinical Considerations section,(www.uspreventiveservicestaskforce.org) but failed to recommend any specific tests over the others," she said. "The (AAFP) subcommittee felt the evidence for the benefits and harms of fecal DNA testing and CT colonography was too limited to recommend these for widespread use."
Consequently, the AAFP has recommended screening for colorectal cancer with fecal immunochemical tests, flexible sigmoidoscopy, or colonoscopy starting at age 50 and continuing until age 75, because these three tests are supported by the best evidence regarding benefits and harms.
The Academy explained in its recommendation that flexible sigmoidoscopy and guaiac-based fecal occult blood testing (gFOBT) are the only screening methods shown to reduce colorectal cancer mortality in randomized controlled trials. Fecal immunochemical tests (FIT) have improved accuracy compared with gFOBT and can be performed with a single fecal specimen.
Optical colonoscopy as a screening strategy can be performed less frequently than flexible sigmoidoscopy or stool-based tests and may detect precancerous lesions that would be missed by these tests. However, the incremental mortality benefit of the test is uncertain, and it is associated with greater harms, the recommendation noted.
And although advanced adenoma detection rates for CT colonography and FIT-DNA testing appear comparable to those of colonoscopy based on cross-sectional studies, both of these screening methods have insufficient evidence of harms.
"CT colonography exposes patients to radiation, and there is insufficient evidence about the harms of associated extracolonic findings, which are common (occurring in 40 percent to 70 percent of screening examinations)," the recommendation said.
FIT-DNA has a higher false-positive rate than FIT, as well as a higher rate of unsatisfactory samples than FIT. Moreover, information is lacking on appropriate screening intervals and follow-up intervals for patients who have a positive FIT-DNA result but a negative colonoscopy.
"The AAFP will relook at fecal DNA testing and CT colonography once there is more evidence available," Frost said.
Grade Difference Has Little Effect
Frost said the subcommittee's assignment of a "B" rather than an "A" grade to this recommendation won't affect family physicians in their daily practice because both grades indicate the service should be offered to eligible patients.
"The subcommittee agreed that the benefits of colorectal cancer screening outweigh the harms, but there are still many unanswered questions about both the benefits and harms, so the recommendation was downgraded to a 'B' grade," she said.
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