Is Mammography still the best?
By Jeff Levine
Reviewed By Pamela Yoder
March 8, 2001 (Washington) -- Despite its flaws, traditional mammography remains the best way of finding a deadly breast cancer. That's the primary conclusion of an expert panel that reviewed 17 other detection systems, including computer-aided approaches like digital mammography.
"With all of its limitations, film mammography remains the gold standard against which new imaging technologies will be measured," says Joyce Lashof, MD, of the School of Public Health at the University of California at Berkeley. "But screening mammography cannot eliminate all deaths from breast cancer, because it does not detect all cancers."
Lashof chaired a panel of experts that reviewed mammograms, the standard breast X-rays, as well as some of the newer and highly touted imaging techniques designed to reveal breast cancer.
"To date, no quantum leap has been made in this area. At the same time, many of the newer tools offer certain advantages and deserve to be studied further," Lashof says.
The analysis, done by the Institute of Medicine (IOM), an arm of the National Academy of Sciences, points toward several different tools including digital, or computer-enhanced, mammograms, ultrasound, and magnetic resonance imaging.
In its report titled, "Mammography and Beyond, Developing Technologies in the Early Detection of Breast Cancer," the panel notes that, "The immense burden of breast cancer, combined with the inherent limitations of mammography ... have been the driving forces behind the enormous efforts ... for the early detection of breast cancer."
It's estimated that more than 180,000 new cases of breast cancer will be diagnosed in the U.S. every year, and more than 40,000 women will die from the disease. While the report notes that the death rate is declining slightly, at least in part due to early detection through mammography, there is considerable room for improvement.
Most of the suspicious findings that are detected via mammography turn out to be benign. That can lead to unnecessary or overtreatment. And even in women with the disease, screening drops the death rate by no more than 40% in those aged 50 to 70.
Barnett Kramer, MD, MPH, director of the Office of Medical Applications Research at the National Institutes of Health, tells WebMD that the IOM mammography report is on target in that it's the only screen that's been shown to lower the death rate.
"The hopeful part is that there are other technologies emerging that haven't been proved to the extent that standard mammography has, but they're certainly worthy of continued study and may replace mammography," says Kramer, who's also the senior medical scientist at the National Cancer Institute (NCI).
Among the existing alternatives is digital mammography. It uses equipment similar to the old machines, except that the images can be displayed and manipulated on a computer. Backers of the high-tech device point out that the greater detail in the image may reduce the need for additional screenings in some cases and that new software could more clearly reveal potentially worrisome changes in the breast like calcifications.
"Many consider [digital mammography] to be a major technical advance over traditional mammography, but studies to date have not demonstrated a meaningful improvement in screening accuracy," the report says. The FDA approved one digital mammography device last year.
Panel member Janet Baum, MD, associate professor of radiology at Harvard Medical School, says the jury's still out on digital mammography.
"It may be better information to some patients [with dense breasts]," Baum tells WebMD.
There also are other alternatives that may prove effective as screening tools, such as high-frequency ultrasound waves that bounce off the tissue and can then be assembled into a map. A new 3-D ultrasound displays tissue in depth, not just a single slice.
Magnetic Resonance Imaging, or MRI, has been used to look inside the body with great accuracy since the mid-80s. Now it might be used to seek out breast tumors that require minimal surgery. Still, this approach may not be as effective in separating out nonmalignant vs. malignant tumors.
For decades, researchers have thought it would be possible to illuminate cancers by shining a light source against the breast and looking at the differences in wave transmission through the tissue. The latest effort involves using techniques that can measure the chemical and molecular components of the breast.
Another option, this one being developed at Harvard, is a handheld scanner that contains pressure scanners that can be moved gently across the breast. The image is generated in as little as 20 seconds without painful compression of the tissue.
To expedite the development of new breast cancer screening approaches, the panel suggests more studies in a variety of areas, with funding coming from several sources. The report also urges Congress to create greater access to mammography through the CDC's screening program. State legislatures also could pick up some of the tab for more poor women through the Medicaid program, the IOM says.
"We're urging that funding be raised to enable them to reach at least 70% of women who don't have access because they have no method of paying," Lashof tells WebMD.
In addition, the IOM wants to see the development of cancer specimen or tumor banks that can help identify genetic changes or biomarkers in breast malignancies at all stages of development. That could lead to a blood test that might eliminate the need for mammography.
The NCI's Kramer says that it's hard to know when to launch a large clinical trial, particularly since new technologies are always being developed. Whatever the machine, he argues that longer survival is the crucial measure of any screen. "Often the tests are embraced before their medical benefits and harms have been tested," he says.
The panel didn't look at the question of when to begin screening. The federal government currently recommends that women have the procedure every one to two years starting in their 40s. The panel did say, though, that there should be further studies to define more accurately the risks and benefits of mammograms for women over age 70.
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