From OncoLog, October 2004, Vol. 49, No. 10
Mammography vs. Magnetic Resonance Imaging: A Breast Cancer Prevention Specialist and a Radiologist Weigh in on the Recent Debate
by David GallowayRecent news reports have some women questioning whether mammographic screening for breast cancer has been made obsolete by magnetic resonance imaging (MRI). The answer is quite simply no, according to Therese Bevers, M.D., an associate professor in the Department of Clinical Cancer Prevention at The University of Texas M. D. Anderson Cancer Center.
The question arose from reports about a Dutch study published in the New England Journal of Medicine in July. “The study that was done actually looked at women at increased risk and divided them into three groups,” said Dr. Bevers, a breast cancer prevention specialist who is also director of the Cancer Prevention Center at M. D. Anderson. “One group was women with a known genetic predisposition, BRCA1 or BRCA2. Another group was high risk but without an inherited predisposition. And the third group was moderate risk, higher than average but not as high as the others. The only population that MRI showed a benefit for was women with an inherited mutation. But it really didn’t get translated that way in the press, so what a lot of women heard was ‘MRI is better than mammography.’”
In truth, the study found that for screening in those women with the known genetic predisposition to breast cancer, MRI may have a role, but only in addition to mammography. “MRI certainly should not take the place of mammography,” Dr. Bevers said.
According to Gary J. Whitman, M.D., an associate professor in the Department of Diagnostic Radiology, “MRI should not be used instead of mammography because mammography finds some cancers that are not identified with MRI.” For example, in the Dutch study, MRI detected 32 breast cancers but missed 13; eight of the 13 cancers missed by MRI were found on mammography, including five cases of ductal carcinoma in situ (DCIS).
MRI is not good at detecting DCIS, the earliest form of breast cancer. “Mammography is really quite good at that,” Dr. Bevers said. “So if MRI were used in place of mammography, it could miss a lesion that, with treatment, is essentially curable.” On the other end of the spectrum, MRI leads to many false-positive findings in various areas of the breast in response to cyclic hormonal changes.
“If women do undergo breast MRI, the studies should be performed at centers capable of performing MRI-guided needle localizations and MRI-guided core needle biopsies,” Dr. Whitman cautioned.
Sonography is another imaging modality drawing considerable interest in screening for breast cancer. It already is widely used in diagnosis and staging, but its role in screening is not yet clear. M. D. Anderson is participating in a multiinstitutional study of sonography as an adjunct to mammography in screening for breast cancer. Dr. Whitman is the principal investigator for M. D. Anderson in the study, which is seeking 2,808 high-risk women at 20 institutions.
In recent years, studies have raised concerns about the limitations of mammographic screening for breast cancer, including the detection of clinically irrelevant DCIS, which can lead to overtreatment; the use of ionizing radiation; and a somewhat high false-positive rate. Despite these concerns, mammography in conjunction with physical examination is still the preferred method of screening for breast cancer.
However, the United States is facing what Dr. Bevers calls a national crisis in the availability of screening mammography. “It’s an area that not many radiologists are going into, and not many radiology facilities want to do it,” she said, citing the high legal liability arising from failure to diagnose an existing cancer and the fact that the cost of mammography is much higher than the Medicare reimbursement rate. Some proposed solutions to the problem include lobbying for higher Medicare reimbursements and having nonphysician radiology interpreters do the initial screening. Whatever it takes to overcome this crisis, Dr. Bevers believes it will come from physicians. “We need to be part of the solution,” she said.
For more information on this topic or for questions about M. D. Anderson’s treatments, programs, or services, call askMDAnderson at (877) MDA-6789.
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