FDA Panel Backs First Digital Mammography System
Dec. 17, 1999 (Rockville, Md.) -- An FDA advisory panel unanimously backed
approval for what stands to be the first available digital device for breast
cancer screening and diagnosis. GE Medical Systems' Senographe 2000D is a
"full-field" digital mammography system.
Brian Garra, MD, chairman of FDA's Radiological Devices Panel, tells WebMD,
"We have enough data to convincingly demonstrate that the digital [system]
is at least as good [as traditional mammography] and will probably advance well
Current mammography practice is centered around analog film images, but
digital technology permits speedier turnaround, easier storage, and physician
manipulation of images.
According to the FDA, about 25 million women are screened for breast cancer
each year, with about 180,000 cancers detected.
"We're seeing now the collapse of the old film-based system. It served
us well for 60 or 70 years," Garra says. "[Digital technology] will
take mammography from the 75% accuracy that we're seeing routinely these days
to maybe 85% or 90%."
Two GE studies, each involving over 600 women, compared mammography readings
from both film and digital systems. Investigators found the technologies
comparable for the detection of cancer, with the new technology requiring
slightly fewer recalls. A separate analysis found comparability between the two
technologies' images of tissue at the chest wall, while the digital application
showed a slight advantage in the visibility of tissue at the skin line.
But the FDA raised a few concerns. Agency reviewer William Sacks, MD, noted
that the relatively low sample sizes the company presented raised the
statistical possibility that the digital technology could be 10% less sensitive
than current applications in detecting cancers -- or 7% more sensitive.
The FDA also said it was concerned that the study may have favored women
with larger or more advanced cancers, since it drew from a population that
included those already screened. But well more than half of the cancers the
digital device detected were early stage -- "type 0" and "type
1" -- exceeding federal clinical guidelines.
Although the FDA wants the company to conduct a post-marketing study to
increase its confidence in the device, the committee thought that that could be
a waste of time and money. Panel member Steven Harms, MD, said, "I have a
great deal of concern whether this is worth the effort," since, he said,
research has already demonstrated digital-traditional film equivalence.
Company officials said they expected the FDA would approve the system
"very early" next year.
To meet regulatory guidelines for testing, GE's clinical research compared
"hard-copy" digital images -- those printed out onto film -- to the
traditional film images. So the firm must still develop and conduct a study of
the effectiveness of the device in "soft-copy" applications -- and sell
the FDA on its findings.
Soft-copy images are those that appear only on a computer screen. That
application permits a radiologist to use a high-resolution monitor and make
adjustments for contrast and light intensity. The advisory panel unanimously
urged the FDA to expedite approval of the soft-copy use.
GE says that it spent 11 years and more than $100 million to develop the
technology. Several other major device firms have digital screening tools in
development, including Siemens Medical Systems, Fischer Imaging, Trex, and Fuji
FDA usually follows, but is not bound by, the recommendations of its