New
guidelines on colorectal cancer recommend shift of focus to comprehensive
initial screening of patients age 50 years and older
New colorectal cancer screening and surveillance
guidelines published by the U.S. Multisociety Task Force on Colorectal
Cancer stress the importance of initial screening for people age 50
years and older and reduce the frequency of surveillance for the majority
of patients who have had colon polyps removed. The updated guidelines
are published in the February issue of Gastroenterology.
Studies suggest that initial colorectal cancer
screening provides the best results. A patient’s first screening
detects the largest, most dangerous polyps, which can be removed
with colonoscopic polypectomy. Previous guidelines recommended that
after polypectomy, patients should receive follow-up colonoscopies
every 3 years. However, data show that follow-up colonoscopies after
3 years may not add significant benefit to many patients because
polyps with important pathology are very unlikely to develop in
that time period. The new guidelines recommend patients who have
1 or 2 small (less than 1cm) tubular adenomas have their first follow-up
colonoscopy at 5 years. Patients with advanced or multiple adenomas
(3 adenomas or more) should still have their first follow-up colonoscopy
at 3 years, the same as recommended in previous guidelines.
"Planning follow-up surveillance of patients
according to their risk for advanced adenomas is an especially important
point in the new guidelines," stressed Sidney Winawer, M.D.,
lead author of the guidelines. "If adopted nationally, this
would shift critical resources from surveillance to screening, helping
us screen more people, which would in turn decrease incidence and
mortality rates."
In addition to recommending risk stratification
for post-polypectomy patients, the new guidelines differ from the
earlier version in emphasizing colonoscopy for screening and surveillance.
Colonoscopy is recommended instead of barium enema for diagnostic
evaluation, for screening people with close relatives who have colorectal
cancer or adenomatous polyps younger than age 60 years, for screening
people with two affected close relatives, for screening people with
possible genetic mutations predisposing them to colorectal cancer,
and for surveillance after polypectomy or colorectal cancer resection.
"Colonoscopy allows us to visualize the
entire colon, and to detect and remove polyps in one procedure.
It’s invaluable in patients who are at high risk of developing colorectal
cancer," said Douglas Rex, M.D., member of the Task Force.
Genetic counseling should guide genetic testing
and considerations of colectomy for patients with family members
carrying mutations. For instance, patients with familial adenomatous
polyposis have a long-term cancer risk that approaches 100 percent.
Family members of an affected patient who test negative are considered
at average risk for colorectal cancer. Family members who test positive
should be followed by sigmoidoscopy until they develop polyps, at
which point the timing of a colectomy can be considered. Genetic
testing in children can be delayed until age 10 years.
Yearly fecal occult blood testing is recommended for people age
50 years or older who are at average risk for colorectal cancer.
Rehydration is not recommended: Although rehydration of the guaiac-based
slides increases sensitivity, the readability of the test is unpredictable
and substantially increases the false positive rate.
Guideline authors looked to the future with
two new tests that are in development. Virtual colonoscopy (thin-section,
helical computed tomography followed by off-line processing) can
yield high-resolution, 3-dimensional images of the colon. Although
the procedure is less invasive and has not caused major complications,
its ability to detect colon polyps is not well established. It requires
the same patient preparation as colonoscopy but neither biopsy nor
polypectomy can be done. In addition, a new DNA stool test is under
study that might be more sensitive than occult blood testing, but
less so than colonoscopy.
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