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Research Highlights
Flat growths that elude colonoscopy
may account for many cancers
March 13, 2008
A study
including more than 1,800 patients at the VA Palo
Alto Health Care System suggests that flattish abnormal
growths in the colon—considered until recently to be rare in
the U.S. and generally ignored during colonoscopies—are more
common than previously thought. Moreover, they are nearly 10
times more likely to be cancerous than polyps—the small raised
knobs of tissue that often contain or signal cancer and are the
main target for detection and removal during colonoscopies.
The research is published in the March 5 Journal of the
American Medical Association, accompanied by an online video
showing the VA team’s innovative detection methods.
Lead author Roy M. Soetikno, MD, MS,
says the new study suggests that flat or
depressed growths—known as nonpolypoid
colorectal neoplasms, or NP-CRNs—may
account for many of the lesions that are
overlooked during colonoscopies in the U.S.
and later develop into cancer. Colorectal
cancer, one of the deadliest forms of cancer,
kills more than 55,000 Americans each year.
Experts believe many cases involve patients
who fail to undergo recommended screenings.
But studies also show that .3 to .9 percent
of patients who undergo a colonoscopy
and have all their intestinal polyps removed
will nonetheless develop invasive cancer
within three years.
Findings likely to have impact on
colorectal-cancer screening
Colonoscopy, considered the gold standard
for screening and early detection of
colorectal cancer, uses a long, flexible tube
fitted with a miniature video camera and
cutting tools. Gastroenterologists use the
procedure to hunt for polyps. These small
outgrowths from the intestinal or rectal wall
are generally removed and biopsied because
they often contain cancer cells, or are likely
to develop into cancer.
Until now, non-polyp growths—also
linked to cancer—have been considered
rare outside Japan. But a few recent studies
show that people in places like Europe and
North America may also be affected. The
new VA study, according to the authors,
is the "largest cohort of patients in which
NP-CRNs have been formally evaluated in
a non-Asian population."
David Lieberman, MD, of the Portland
VA and Oregon Health and Science University,
widely known for his research on
colonoscopy and cancer detection, wrote an
accompanying editorial in which he said,
"It is now clear that both Asian and Western
populations may develop NP-CRNs." He
told the Associated Press, "This paper will
have a big impact on gastroenterology. It
will heighten people’s awareness that, yes,
these are found in the United States."
The study included 1,819 male veterans,
mostly white, who underwent a colonoscopy
in 2003 or 2004. About a third of the
procedures were for routine screening. The
others were because of symptoms such as
rectal bleeding or diarrhea, or because of a
family or personal history of colon polyps
or cancer. Most of the lesions found were
polyps: 594 men had only polyps, 89 had
only NP-CRNs, and 81 had a combination.
But the presence of NP-CRNs in 170 of the
men, for a prevalence of 9.35 percent, suggests
the problem is far more widespread
among Americans than previously thought.
And even though the flat or depressed
growths represented only about 15 percent
of the lesions found, they proved nearly 10
times more likely to harbor cancer, accounting
for more than half the malignant tumors
found.
Learning from Japanese doctors
Through a faculty-exchange program
with Japanese endoscopy centers, Soetikno’s
team developed expertise in detecting
the NP-CRNs, which are harder to spot than
their raised counterparts, the polyps. “They
look like a pancake just lying on the floor,”
said Soetikno. The physician-researchers
studied colonoscopy videos showing flattish
or depressed growths and learned how
to spray a reddish dye inside the colon to
highlight their subtly abnormal texture. The
specialized methods have been used at the
Palo Alto VA since 2000, and Soetikno and
his colleagues expect they will now become
more widespread in VA and other medical
centers.
This article originally appeared in the March 2008 issue of VA Research Currents.
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