April 27, 2010 --
Colon cancer screening with just one flexible sigmoidoscopy cuts cancer risk and identifies those who
need more invasive colonoscopy, an 11-year U.K. study finds.
The study looked at more than 17,000 men and women ages 55-64 who said they
were willing to take a
colon cancer screening test.
That test: flexible sigmoidoscopy, an exam that requires a
similar night-before bowel prep as a colonoscopy but which is much simpler
and less risky to perform. While colonoscopies usually are performed
with anesthesia and by a gastroenterologist, sigmoidoscopies require
no sedation and can be performed by general practitioners or trained
The downside of sigmoidoscopy is that it can see only the left side of the
colon. Can that really be enough to prevent colon cancer?
Yes, find Wendy S. Atkin, PhD, MPH, of Imperial College, London, and
colleagues. Atkin's team was looking for a cost-effective way to screen the
entire U.K. population for colon cancer. Early studies suggested that just a
single sigmoidoscopy around age 60 could prevent colon cancer.
How? Sigmoidoscopy is just as good as colonoscopy at finding and removing
colon polyps in the left side of the colon, where two out of three
colon cancers arise. Atkin's research suggested that a look at the left colon
can identify the minority of people who need a full colonoscopy -- and that it
can also identify the majority of people who will never need another invasive
colon screening test.
Now it seems that all this may be true. Eleven years later, people who
got that single sigmoidoscopy had 33% fewer colon cancers and 43% fewer deaths
from colon cancer.
"It's a one-off test ... and it probably will be done just once in a
lifetime," Atkins said at a news briefing. "It works well to prevent cancer in
the [left] bowel. We don't think it can prevent cancers higher up in the bowel,
but we can detect them early using the existing [fecal occult blood] test."
Moreover, the study finds that colon cancer risk continues to decline in the
years following flexible sigmoidoscopy.
"You'd think by now we'd see some sign of waning protection, but we see no
waning at all," Atkin said. "I hypothesize it will last forever because I
believe most of the polyps that are going to cause [left bowel] cancer are
already there in your 50s. So all we have to do is look for them, find them,
and remove them. And so far this hypothesis seems to be playing out."
Atkins and colleagues argue that in the government-funded U.K. health
system, a single sigmoidoscopy at age 60 plus regular fecal occult blood test
(a simple test for blood in the stool) will cut the colon cancer rate while
lowering overall health care costs.