TUESDAY, May 10 (HealthDay News) -- Colonoscopy is significantly
better than the less expensive screening procedure called
sigmoidoscopy at detecting colon cancer in older patients, a new
"We imagined there would be some difference, but there's a four-fold difference" between the two screening tests when it comes to detecting cancer, said study lead author Dr. Yize Richard Wang, a fellow at the Mayo Clinic in Jacksonville, Fla.
"Colonoscopy still remains the gold standard," added Wang, a health economist.
In the United States, colon cancer kills more than 51,000 people
a year, according to the National Cancer Institute. Screening helps
identify cancer before symptoms appear, when it may be easier to
Colonoscopy, the most common screening test for colon cancer,
involves threading a scope with a tiny camera through the length of
the colon. But patients can also choose flexible sigmoidoscopy,
which uses a shorter scope, costs less and may be more comfortable.
However, sigmoidoscopy examines only half or less of the colon,
Years ago sigmoidoscopy was the main screening test for colon
cancer, but it has become less common over time. However, "from a
patient perspective, the preparation and discomfort associated with
a sigmoidoscopy is often considered less burdensome," said Dr.
Thomas Semrad, assistant professor of internal medicine at the
University of California, Davis Medical Center, who's familiar with
the study findings.
Using a national database, the study authors examined the
records of 52,236 patients 67 or older who underwent colonoscopy or
sigmoidoscopy between 1998 and 2005 and were diagnosed with colon
cancer within three years of the procedure. According to the study
abstract, 57,412 colonoscopies were performed, as were 3,523
The percentage of new or missed left-sided colon cancers was 12
percent among the sigmoidoscopy patients but only 4 percent for the
It's not clear why colonoscopy was better at detecting cancers,
Wang said, but it may be because the sigmoidoscopy misses part of
"If you suspect the patient has colon cancer, colonoscopy is still a better test than flexible sigmoidoscopy," he said.
Differences in bowel preparation and lack of sedation might also
help explain the variation, the study authors said, noting further
research is necessary.
The study was to be presented Tuesday at the Digestive Diseases
Week conference in Chicago. The research is considered preliminary
because it has not been subject to the scrutiny required for
publication in a peer-reviewed journal.
Although the study did not include people younger than 67, "the
results might be similar," Wang said.
Semrad said sigmoidoscopy may be appropriate in some cases.
Compared to a colonoscopy, "an individual sigmoidoscopy will cost
less, be easier to perform, and in the right hands can be an
appropriate screening test," he said.
"Ultimately, the right test will be different for different patients and different health systems," Semrad added.
The U.S. Preventive Services Task Force recommends colonoscopy
screening every 10 years for people 50 to 75 years old who are
considered at average risk of getting colon cancer.
It's important that people undergo screening, Semrad said. "We
know that we could save thousands of lives each year if everyone
was screened according to the guidelines," he added.
But some people have a fear of the procedure, he noted. "Because
the preparation is easier and the discomfort is often less,
[sigmoidoscopy] can be especially important testing for patients
unwilling to undergo colonoscopy," he noted.
For more about
colon cancer, visit the U.S. National Library of Medicine.
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