Reporting from Washington — Three-dimensional mammogram technology, which could reduce the number of women who need additional screening for breast cancer, received approval Friday from the Food and Drug Administration.
But experts and advocacy groups were divided over how helpful the new images would be.
About 10% of women require follow-up screening because their first set of mammograms is not clear enough, which 3-D images might help resolve, said Kristin Byrne, chief of breast imaging for New York's Lenox Hill Hospital.
"I think it'll help us with patients that have dense breast tissue," said Byrne, predicting that 3-D imaging for breast cancer screening eventually will become standard.
But Carol Lee, chairwoman of the American College of Radiology's committee on breast imaging, said it's too early to tell how useful the technology will be.
Studies show that 3-D imaging is as good as 2-D imaging in detecting cancerous growths, and that it helps decrease "false positives" — abnormalities that turn out to be noncancerous. That, in turn, could reduce the number of needless biopsies.
"But it hasn't been shown that it picks up more cancers," Lee said. "It may, but that hasn't been shown yet."
Once the technology becomes widely available, it would presumably reduce the number of initial mammograms that yield inconclusive results, thus reducing follow-up tests. But whether that would reduce breast cancer deaths was not clear.
Today, breast cancer claims the lives of about 40,000 people in the U.S. each year, most of them women. But the survival rate is 98% when the disease is detected early and localized to the breast.
The FDA approved the Selenia Dimensions System, marketed by Hologic Inc. of Bedford, Mass., which produces both conventional digital 2-D mammography images and 3-D images. The FDA required that 3-D images be taken in tandem with 2-D images.
Both images are required because that's the way Hologic designed studies showing the effectiveness of its technology, according to FDA spokeswoman Erica Jefferson.
"There was no comparison of 3-D versus 2-D alone," Jefferson said in an e-mail.
"As technology improves and radiologists become more familiar with the 3-D imaging technology, FDA could be in a position to approve a device that is just intended for 3-D imaging," Jefferson said.
Hologic marketing director Jim Culley said the company sought a combined 2-D and 3-D approval because it recognized that doctors had spent years learning to read 2-D images and didn't want to introduce a completely new system.
"We wanted to make this as easy as possible," said Culley, adding that 40 countries have approved the device.
Lee, of the American College of Radiology, said the 3-D imaging delivers more radiation to patients than standard 2-D mammography and that it takes more time for radiologists to interpret results.
The Selenia system delivers about twice the dose of radiation as a conventional series of mammograms, the FDA said, but its improved accuracy decreases the number of women called back for additional screening.
Cindy Pearson, executive director of the National Women's Health Network, said 3-D mammograms need to develop a track record before their value can be assessed.
"I don't believe that anything FDA was able to examine in advance would tell women that this is more likely than existing mammography to save their life or avoid disfiguring treatment," Pearson said. "It's going to be a while before we find out if it makes a difference. I wouldn't rush out and get one."
The units cost about $500,000 — $150,000 more than a conventional 2-D machine — and are expected to add about $4 to the cost of a mammogram, Culley said.
Laura Nikolaides, director of research and quality care programs for the National Breast Cancer Coalition, said the new technology would be of no use in combating the most lethal cancers.
"We don't need more expensive imaging equipment," Nikolaides said. "What we need are more sophisticated ways to screen breast cancers" to identify the most virulent ones earlier.