WEDNESDAY, July 28, 2004 (HealthDayNews) -- For a small subset of women with a genetic or family predisposition for breast cancer, regular MRI breast screening may be the best way to spot tumors early.
Breast MRIs conducted annually were nearly 80 percent effective in picking up invasive cancers in high-risk women, compared to the 33 percent effectiveness rating of annual mammographies, Dutch researchers report in the July 29 issue of the New England Journal of Medicine.
However, experts agree that MRI's high rate of false positive results -- findings that could be malignant tumors, but turn out to be benign -- make the technology much less desirable for women at normal breast cancer risk.
While regular MRI breast scans may be of benefit to women at high risk, "women at normal risk should not be encouraged to undergo regular MRI screening," said study author Dr. Jan G. M. Klijn, a medical oncologist at the Rotterdam Family Cancer Clinic.
Breast cancer remains the second leading cause of cancer death among American women. While mammography is moderately effective in spotting tumors, a small percentage of women -- such as those carrying the BRCA1 or BRCA2 breast cancer genes -- may need screening technologies with even greater powers of detection.
"In their lifetime, 50 to 85 percent of these women will develop breast cancer," explained Dr. Laura Liberman, attending radiologist in the Breast Imaging Section at Memorial Sloan-Kettering Cancer Center in New York City.
Liberman, who wrote an editorial accompanying the Dutch study, said that for these women, an annual mammogram just isn't enough. "So, people are now studying supplementary techniques, such as MRI," she said.
In their study, Klijn's team selected 1,909 adult women who were either carriers of the BRCA1 or BRCA2 genes, or who had a strong family history of breast cancer -- defined as close relatives diagnosed with breast tumors before age 30.
All of the women received clinical breast exams every six months, plus mammography and MRI screening annually, over the course of three years.
Fifty-two breast cancers were detected among the group during the study period, the researchers report. In terms of early detection, MRI far outperformed mammography or clinical breast exams, with detection rates calculated at 79.5 percent, 33.3 percent and 17.9 percent, respectively. MRI was also much better at detecting very small tumors (10 millimeters or less in diameter) at a very early stage.
Based on the findings, Klijn said, "our recommendations are to use MRI as a screening method in specialized facilities, for women with a BRCA 1/2 mutation or a really high risk of breast cancer."
Both Klijn and Liberman are careful to not extend this recommendation to women at average risk, however.
Liberman explained that, besides the scarcity and high cost of MRI, the technology's strength -- its ability to spot very tiny abnormalities in tissue -- is also a weakness.
"This is a very sensitive test -- if there's a cancer hiding in the breast, it's likely to show up," she said. "But as a tool it's also not very specific -- meaning that a lot of normal stuff will light up, too."
That may be acceptable for the anywhere from 1 percent to 10 percent of women at very high risk for breast cancer, she said. For these women, "if you have a positive result, the likelihood that it's a [a tumor] is so much higher" that it may be worth going to the next step, which is biopsy, Liberman explained.
On the other hand, MRI's high false-positive rate "would simply cause a lot of anxiety and then lead to a lot of unnecessary, benign biopsies if we started to apply it as a screening test in the general population," she said. "There's just no evidence that it's a helpful screening test in women at normal risk."
Learn about the early detection of the disease from the American Cancer Society.