MRI evaluation of the contralateral breast in women recently diagnosed with breast cancer

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. Of these, 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. After receiving an MRI, 33 contralateral breast cancers were diagnosed in the study. Thirty of these tumors, or 91 percent, were diagnosed as a result of MRI. The other three cancers were detected due to subsequent mastectomies. Researchers found that the added benefit of MRI was consistent, regardless of a woman's cancer type, age, or breast density. Dense breasts have more glandular and connective tissue as well as less fat tissue.

"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 hope 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.

Researchers are optimistic that there may be long-term savings to patients and to the health care system due to MRI's ability to detect cancer in both breasts prior to therapy -- which may result in fewer rounds of chemotherapy and breast surgeries.

Constantine Gatsonis, Ph.D., the study's statistician and director of Brown University's Center for Statistical Sciences, Providence, R.I., said, "The size and scope of this study -- which followed nearly a thousand women receiving care in a variety of medical settings -- means that its findings are definitive and broadly applicable. Women can be assured that a negative MRI means that their chance of having a second cancer diagnosed within a year is miniscule."

For most women, the fear of a second cancer diagnosis is quite high. The researchers hope that breast MRI can improve a woman's quality of life both at the time of her diagnosis and the years following.

In the United States, breast cancer is the most frequent newly diagnosed non-skin cancer in women, and the second leading cause of cancer-related death. An estimated 178,480 women will be diagnosed with breast cancer and an estimated 40,460 women will die of the disease in 2007.