Trials show no advantage in digital mammography over traditional film
Digital mammography devices were only approved for use in the USA five
years ago. Since then tens of thousands of women each year have had scans
with the new technology, which is far more expensive than the traditional
film X-rays. To be cost effective, significant improvements in detection of
breast cancer would be expected. A new technology assessment report,
however, says that digital mammography provides no clear-cut improvements
over traditional film X-rays in the ability to detect cases of breast
cancer. The technology does, though, offer other benefits, including
slightly lower radiation doses for patients, that may prompt its increasing
use despite its much higher costs.
Known as “full-field digital mammography,” the high-tech equipment
records images of the breast electronically instead of on X-ray film. The
pictures are stored directly in a computer system, where they can be
enhanced, magnified or shared. The digital devices were first approved for
marketing in the United States in 2000.
Three large trials of the technology have been completed, with several
thousand women receiving digital mammograms in each. No statistically
significant differences in detection rates were observed between the x-ray
and the new digital technology. The patients in each group experienced
identical positioning and compression of the breast.
“The studies that have been done so far haven’t provided a ‘slam-dunk’
for full-field digital mammography,” says Robert Maliff, associate director
of the Health Systems Group at ECRI, whose Technology Assessment Group
published the report. ECRI is a nonprofit health services research agency
that produces systematic evidence reviews on medical devices, drugs,
biotechnologies, procedures, and behavioral health services.
Maliff says radiation for patients may be “incrementally lower” with
digital screening depending on the type of detector used, but the report did
not assess the literature on radiation doses — rather it assessed its
efficacy as a screening technology for breast cancer.
A new large clinical trial sponsored by the National Cancer Institute has
recently been completed, and published results are expected soon. Nearly
50,000 women in the United States and Canada received both types of
mammograms and were asked to return one year later for follow-up exams to
determine whether digital mammography detects breast cancer more accurately
At best, the new technology is expected to offer incremental improvements
in cancer detection rates, which Maliff says may be enough to spark a
large-scale transition to the new technology.
“Cost-effectiveness will ultimately determine whether full-field digital
mammography technology is adopted, since hospitals must justify their
purchase based on exam volume and patient population,” the report says.
Digital mammography systems cost at least three times as much as film
systems. In addition to reducing radiation, they can also facilitate the use
of computer-aided detection systems and can be easily transmitted for second
opinions, according to the report. The technology lends itself to
operational improvements. Without films to process, handle, and store,
radiology workflow becomes more efficient, says Maliff.
“Many health care professionals predict that screen-film mammography will
eventually be replaced by full-field digital mammography once it is proven
that the image quality and diagnostic accuracy of both technologies are at
least equivalent,” says the ECRI report.
According to ECRI, the current body of evidence that suggests that
digital mammography may be able to reduce recall rates, and possibly
necessary follow-up procedures, which could offset some of its higher
initial costs. But more evidence is needed to confirm these potential
Maliff predicts some facilities may “take the leap” to digital
mammography for marketing reasons to position themselves as offering the
best women’s care services.
Breast cancer is the most common malignancy in women and the third most
frequent cancer throughout the world. More than 1 million new cases were
diagnosed worldwide in 2002, and incidence rates are increasing at about 5
percent a year.
Source: Health Behavior News Service:
www.hbns.org of the
Center for the Advancement for Health:
Contributing Writer, Laura Kennedy