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March 4, 2008 -- Ten years after the first high-tech computerized device to help with breast cancer screening hit the U.S. market, researchers and regulators are still trying to figure out just how useful they are.
An FDA advisory panel heard testimony today about the effectiveness of computer-aided detection, known as CAD. Thousands of clinics and radiologists' offices now use the devices; the idea is to help improve the chances that suspicious areas on mammograms won't go unnoticed among the thousands of women who get screened for breast cancer each day.
Hundreds of studies have been done on CAD since the FDA approved it in 1998. But many are small or contain biases. Some studies suggest that CAD may improve a radiologist's chances of catching a hard-to-see cancer. But others have not shown better accuracy in computer-aided reading of mammograms, including a study published last year.
CAD is vulnerable to false-positives: red flags that turn out not to be cancer. That can lead to unneeded office visits, invasive biopsies, and lots of anxiety for worried patients. But the companies that make CAD products say their machines improve detection with only minimal false-positives. And some radiologists back them up.
Part of the problem is that the vast majority of women who get routine breast cancer screening don't have cancer. That leaves radiologists to sort through mountains of "noise" in an effort to catch cancers early.
"The task of the mammographer is essentially to find a needle in a haystack," Akira Hasegawa, an executive with Fujifilm Medical Systems USA, told an FDA advisory panel Tuesday.
CAD doesn't replace a human radiologist. Instead, it uses a computer algorithm to "mark" potentially worrisome areas and draw doctors' attention to them.
Doctors sometimes don't find?cancers, said Robin Birdwell, an associate professor of radiology at Brigham and Women's Hospital at Harvard Medical School.?
"Having a tool to improve sensitivity is a good idea," said Birdwell, who represents the Society for Breast Imaging, a group that receives industry funding.
And this "good idea" is why researchers lament that few independent studies are large enough or designed properly to answer the lingering questions about the technology.
Researchers said they want the government to accelerate an effort to build a massive database of mammography results to help researchers run unbiased tests of how computer-aided screening stacks up against humans alone in the real world.
"CAD works. It works well in certain specific areas," said Carl J. d'Orsi, MD, a professor of radiology at Emory University and a member of the FDA's advisory panel.
"I think we have to define more where it is good and where it is not good," he said.
Researchers already know that false-positives can cause a lot of anxiety in women who fear they may have cancer when they don't. What they don't know is whether most women are willing to risk anxiety and more biopsies in exchange for better cancer detection, said David K. Spindell, MD, vice president of medical affairs at Abbott Pharmaceuticals and a panel member.
"That question really has to be flushed out," he said.