Magnetic Resonance Imaging (MRI) scans of women who were diagnosed with cancer in one breast detected over 90 percent of cancers in the other breast that were missed by mammography and clinical breast exam at initial diagnosis, according to a new study. Given the established rates of mammography and clinical breast exams for detecting cancer in the opposite, or contralateral breast, adding an MRI scan to the diagnostic evaluation effectively doubled the number of cancers immediately found in these women. The American College of Radiology Imaging Network (ACRIN) study, supported by the National Cancer Institute (NCI), part of the National Institutes of Health (NIH), appears in the March 29, 2007 issue of the New England Journal of Medicine.*

"One in ten women diagnosed with cancer in one breast will develop the disease in the opposite breast. Having a better technique to find these cancers as early as possible will increase the chances of successful treatment," said NIH Director Elias A. Zerhouni, M.D.

The ACRIN trial was designed to determine whether the use of MRI could improve upon clinical breast exam and mammography in detecting breast cancer in the opposite breast at the time of the initial breast cancer diagnosis. The study recruited 1,007 women from 25 institutions who had a recent diagnosis of cancer in one breast. 969 women completed the study, which began in April 2003. All of the women enrolled had a negative mammogram and negative clinical breast exam of the opposite breast within 90 days prior to the MRI. Of the 33 contralateral breast cancers diagnosed in the study, 30 cancers, or 91 percent, were diagnosed as a result of MRI. Researchers found that the added benefit of MRI was consistent, regardless of a woman?s cancer type, age, or breast density.

"This study gives us a clearer indication that if an MRI of the opposite breast is negative, women diagnosed with cancer in only one breast can more confidently opt against having a double, or bilateral, mastectomy," said NCI Director John E. Niederhuber, M.D.

"We can now identify the vast majority of contralateral cancers at the time of a woman's initial breast cancer diagnosis," said Constance Lehman, M.D., Ph.D., principal investigator of the ACRIN Breast MRI Trial, professor of radiology and director of breast imaging at the University of Washington and Seattle Cancer Care Alliance. "This means that instead of those women having another cancer diagnosis years after their initial treatment, we can diagnose and treat those opposite breast cancers at the time of the initial diagnosis."

Researchers are hopeful that with breast MRI?s strong ability to predict the absence of a tumor, they can avoid some unnecessary mastectomies and provide women with more reassurance that the breast is disease free. "Although no imaging tool is perfect, if the MRI is negative, the chance of cancer in that breast is extremely low. A potential outcome that we would be delighted to see is fewer unnecessary bilateral mastectomies," said Lehman.