Computer-aided detection
systems may not be as helpful in detecting breast cancers as
earlier studies had indicated.
That's the conclusion
of a new study in the Feb. 4 issue of the Journal of the
National Cancer Institute. It compared the results of more
than 50,000 mammograms examined only by a radiologist, versus
another 50,000 read by both a radiologist and a computer-aided
detection system.
No statistical difference
was found between the two methods. However, the study authors
say more research needs to be done to determine if computer-aided
detection (CAD) saves more lives and is more cost-effective
than screenings using a radiologist alone.
CAD is software
programmed to look for abnormalities on mammograms. In health
centers where the software is in use, mammograms are screened
both by the computer system and by a radiologist. CAD is not
used in place of humans. In previous studies, which were done
in controlled laboratory settings, it appeared that the use
of CAD in addition to a radiologist's interpretation could increase
the rate of cancer detection by as much as 20 percent.
"Clearly, the goal
of this technology was to help detect more cancers earlier,"
says study co-author David Gur, a professor of radiology at
Magee-Women's Hospital of the University of Pittsburgh Medical
Center.
But, he says, at
least in this study, the technology fell short of that goal.
"We are not saying
that CAD is not good, just that in our environment, this technology
did not help in detection," Gur says.
Gur and his colleagues
compared three years of screening mammograms. Just over 56,400
mammograms were interpreted without the use of CAD, and 59,139
mammograms were interpreted with CAD and by a radiologist.
The mammograms were
performed at the clinical breast imaging center at Magee-Women's
Hospital, a high-volume academic center with highly trained
radiologists on staff.
For every 1,000
mammograms studied, breast cancer detection rates were 3.6 percent
without CAD and 3.5 percent with CAD. According to Gur, this
difference is not statistically significant.
Dr. Joann Elmore
is an associate professor of medicine and epidemiology at Harborview
Medical Center at the University of Washington School of Medicine
in Seattle. She finds the study results "a bit of a disappointment."
"These CAD programs
have been approved by the FDA (U.S. Food and Drug Administration)
and the hope is that they will assist us in catching more cancers,
and this study did not show any improvement," says Elmore, who
wrote an accompanying editorial in the same issue of the journal.
Both Gur and Elmore
say the new study highlights the difficulty in assessing the
effectiveness of new technologies. In other settings, such as
a low-volume breast imaging center where the radiologists may
be less experienced, the addition of CAD might be helpful in
detecting more cancer, both point out.
More research needs
to be done on the subject, they agree.
In the meantime,
Elmore says the most important thing women need to remember
is that no screening is foolproof.
"Women need to know
that even with a human radiologist and a backup computer detection
system, cancer can still be missed," she says.
But, she adds, it's
also important for women to realize that most abnormalities
discovered on mammograms turn out to be nothing. "The great
majority of women who have an abnormality on a mammogram don't
have breast cancer," Elmore says.
More information
For more information
on mammograms, go to the National
Library of Medicine.
Reference
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