People who have had a colonoscopy in the past decade are
less likely to be diagnosed with advanced colon cancer than those who haven't
been screened recently, according to a new study.
Researchers found less-invasive tests, known as
sigmoidoscopies, were also tied to a lower risk of advanced tumors - but only
those growing in one side of the colon. It's still not clear what that means
for cancer survival, according to Dr Chyke Doubeni, who led the new study at
the University of Pennsylvania's Perelman School of Medicine in Philadelphia.
But while researchers wait for results from more controlled,
long-term trials, the new report is more evidence that screening in general is
beneficial, they said."There's a variety of screening tests for us to
choose from," Doubeni told Reuters Health. "
How the study was
This study doesn't show that colonoscopy is the only test,
but it does show that colonoscopy has the advantage in being able to see the
right side (of the colon)... unlike sigmoidoscopy and fecal occult blood
testing."The US Preventive Services Task Force, a government-backed panel,
recommends people between age 50 and 75 get screened for colon cancer using
regular fecal occult blood testing, sigmoidoscopy or colonoscopy.
The suggested interval between screenings depends on the
method - from blood tests every year to colonoscopy every ten years. According
to the American Cancer Society, about one in 20 people will be diagnosed with
colon or rectal cancer during their lifetime.
For the new study, Doubeni and his colleagues analysed
records from 474 people with advanced colon cancer and another 538 people
without cancer who were the same age and covered by the same healthcare plans.
The researchers found about three percent of people with
advanced cancer had undergone colonoscopy in the past decade, compared to nine
percent of the cancer-free group. Just under 20% of people with late-stage
cancer had a past sigmoidoscopy, versus 34% of comparisons.
That translated to a 71% lower risk of advanced cancer among
people with a past colonoscopy and a 50% lower cancer risk after sigmoidoscopy.
The pattern held for cancers in both the left and right colon for colonoscopy.
seemed to only prevent advanced tumors on the left side - the easier side to
reach with a scope, the researchers wrote Monday in the Annals of Internal
Medicine. REMINDERS HELPIn another study published alongside Doubeni's report,
researchers led by Dr Beverly Green from Group Health Research Institute in
Seattle found more people were up-to-date with colon cancer screening when they
were reminded about screening tests at times coordinated by electronic health
Doubeni said his team's findings don't mean colonoscopy
should be considered the only, or even best, option for cancer screening.
"It's also about whether people use it or can afford to use it," he
said. Those who dread a colonoscopy so much they keep putting it off would be
better served choosing a less-invasive screening technique, for example.
Experts reported colonoscopy
more effective than sigmoidoscopy
Dr Nancy Baxter, a colon cancer researcher and surgeon from
the University of Toronto, said researchers have expected colonoscopy to be
more effective than sigmoidoscopy - the question is how much more effective,
and is that worth it.
"Colonoscopy is more expensive, it's more risky, it
requires you take the day off work," Baxter, who wasn't involved in the
new research, told Reuters Health. At over $1,000(R9064), colonoscopy is
typically about twice as expensive as sigmoidoscopy.
The new study "emphasises again that colon cancer
screening is effective, and it's highly effective," Baxter said."I
think what's important to see is actually flexible sigmoidoscopy does a pretty
good job too, and if you don't want to go the whole way and do a colonoscopy,
if that's not for you, then a flexible sigmoidoscopy is pretty good too,"