WASHINGTON—Despite some promising new technologies, traditional x-ray film mammography remains the gold standard in screening for breast cancer, a committee of the Institute of Medicine (IOM) has concluded.
The committee’s review included several breast imaging tools already approved for breast cancer detection by the Food and Drug Administration (FDA) and others, such as optical imaging, still in development.
"Several show promise as adjuncts to mammography, but to date, none have been proved to be superior to conventional mammography for routine screening," said committee chair Joyce C. Lashof, MD, professor emerita of the University of California, Berkeley, School of Public Health.
Dr. Lashof said that ultrasound and magnetic resonance imaging (MRI) can aid in diagnosis and may be of value in screening selected groups of women. Digital mammography offers technical advantages, she said, but has not yet been shown to be more accurate than film mammography. "Many other new technologies are at a relative early stage of development, and thus more research is needed to adequately assess their accuracy and effectiveness," she said.
The IOM, part of the National Academy of Sciences, established its study committee in 1999 to look closely at the current state-of-the-art of early breast cancer detection. Funding for the effort came from seven independent foundations and individuals.
The committee expressed concerned that new imaging technologies approved by the FDA for diagnostic purposes were also being used for screening without adequate proof of efficacy.
Both she and Janet K. Baum, MD, noted that only one large trial has compared the breast cancer screening powers of film and digital mammography. Among about 7,000 women, the study found no statistical difference in detection rates, said Dr. Baum, associate professor of radiology, Harvard Medical School, and director of breast imaging, Beth Israel Deaconess Medical Center.
Dr. Baum added, however, that digital mammography has technical advantages over film mammography, including easier image retrieval, storage, and transmission, and easier use with computerized detection systems.
She noted that one hope for digital mammography is that it will improve detection rates in women with denser breasts. A multicenter study to assess that potential, with a planned enrollment of 50,000, will start this summer. The protocol calls for each woman to receive a screening with both film and digital mammography, be rescreened 1 year later, and be followed for a total of 3 years.
Panel vice chair I. Craig Henderson, MD, adjunct professor of medicine, University of California, San Francisco, added that all breast cancers are not the same; to avoid overdiagnosis, it is crucial that researchers learn how to distinguish more virulent from less dangerous tumors.
Recommendations
The committee made several recommendations:
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Government support for development of new breast cancer detection technologies should continue to emphasize research on the basic biology and etiology of breast cancer and on the creation of classification schemes for breast cancer lesions based on molecular biology.
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Breast cancer specimen banks should be expanded, and researchers’ access to patient samples should be enhanced.
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The FDA should develop and apply consistent criteria for approval of screening and diagnostic devices and tests.
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For new screening technologies, FDA approval and coverage decisions by the Health Care Financing Administration (HCFA) and private insurers should depend on evidence of improved clinical outcome.
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The National Cancer Institute (NCI) should create a permanent infrastructure for testing the efficacy and clinical effectiveness of new detection technologies as they emerge.
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HCFA should analyze current Medicare and Medicaid reimbursement rates for mammography screening, including a comparison with other radiologic techniques, to determine whether they adequately cover the total costs of providing the procedure.
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The Health Resources and Services Administration should undertake or fund a study to analyze trends in specialty training for breast cancer screening among radiologists and radiologic technologists, and examine factors affecting the decision of practitioners to enter or remain in the field.
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Until health insurance becomes more universally available, Congress should expand the Centers for Disease Control and Prevention screening program to reach a higher fraction of eligible women, and state legislatures should participate in the federal Breast and Cervical Treatment Act by providing funds for cancer treatment of eligible women.
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The NCI should sponsor large randomized trials every 10 to 15 years to reassess the effect of accepted screening modalities on clinical outcome.
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The NCI, in conjunction with the American College of Radiology Imaging Network or the Breast Cancer Surveillance Consortium, should sponsor further studies to define more accurately the benefits and risks of screening mammography in women over age 70.
