Early last spring, the American Cancer Society issued new guidelines calling for women in certain breast cancer risk groups to be screened via MRI (magnetic resonance imaging), as well as mammography. At the same time, the New England Journal of Medicine, in its March 29 issue, detailed a national study whose results indicated that women who’ve been diagnosed with cancer in one breast should have an MRI in the other, as MRI can detect very early cancers that can’t be seen on a mammogram.
Now, results of a German study published in the August 11 edition of The Lancet, a British medical journal, add a bit more fuel to the fire slowly kindling under MRI as a replacement for mammography. In the study, researchers at the University of Bonn tested over 7,000 women for breast cancer, using both mammography and an MRI. Of those women, 167 were confirmed as having DCIS. And of the 167 women with DCIS, a mammogram detected it in 93, while an MRI identified the pre-cancerous condition in 153 women–a 65% increase in effectiveness.
That’s pretty impressive, eh? Since breast cancer prevention is preferable to breast cancer treatment; and since DCIS (which often leads to invasive cancer) appears SO much more detectable via MRI, why aren’t all women routinely getting MRIs?
Because they also produce an unacceptable number of “false positives,” identifying breast tissue as containing DCIS when it actually doesn’t. The only way to ascertain this, however, is via biopsy. Which is expensive, time-consuming, painful, and stressful.
Bottom line: should hordes of average women, women with no known breast cancer risk, put themselves on the line for a possibly unnecessary biopsy, in order that a small fraction of them will be diagnosed with DCIS? DCIS that a typical mammogram would have caught anyway, more than half the time?
Another strike against MRIs replacing mammograms: on average, they’re about ten times as expensive. Yet another: most hospitals aren’t equipped to deliver screening MRIs to women on a large-scale basis. They have neither the equipment, nor the trained personnel to interpret the results. Certainly, these facts will change over time. If MRI is identified as the screening tool of choice, the market will make its delivery more competitive. If more women demand MRIs, hospitals and cancer centers will equip themselves to offer them. It’s the law of supply and demand, if nothing else. But at the present time, mammography still has a firm hold on the top spot when it comes to current best practices in screening normal women for breast cancer.
Julie Gralow, MD, is chair of the American Society of Clinical Oncology Cancer Communications Committee, and associate professor of medicine/oncology at the University of Washington School of Medicine and Fred Hutchinson Cancer Research Center in Seattle. Summing up the MRI/mammogram standoff, she notes, “Once the quality of breast MRI is established, we will be ready to implement clinical trials to determine whether screening MRI can improve survival without increasing the financial and psychological costs when compared with mammography, which is a standardized screening tool proven to reduce deaths from breast cancer.”
In other words, MRI is taking steps towards replacing mammograms as the screening tool of choice for women without any known breast cancer risks. But the steps are small and tentative, and the path a long one. Don’t ask to substitute MRI screening for your regular mammogram appointment just yet.
Published On: August 28, 2007