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MRI Increases Detection of Second Cancer in Opposite Breast

When a woman is newly diagnosed with cancer in one breast, there’s up to a 10% chance that clinical exams and mammography will miss a tumor growing in the opposite breast. In light of this, some women opt for a prophylactic double mastectomy. Others choose to keep their breast but live with the chance of developing a second cancer. A new study funded by NIH's National Cancer Institute (NCI) provides welcome news to women faced with this decision. It found that magnetic resonance imaging (MRI) improved the detection of cancer in the opposite breast at the time of initial diagnosis.

A team of researchers led by Dr. Constance Lehman at the University of Washington and Seattle Cancer Care Alliance evaluated 969 women from 25 institutions who were recently diagnosed with breast cancer. Clinical exams and mammography showed the women to be negative for cancer in the opposite, or contralateral, breast within 90 days of an MRI. The women were followed for one year, and their cancer diagnosis was confirmed by biopsy.

The researchers reported in the March 29, 2007, issue of the New England Journal of Medicine that, of the 33 contralateral breast cancers detected, 30 of them, or 91%, were diagnosed by MRI. The ability of MRI to detect these cancers was independent of cancer type, age or breast density.

The researchers explained that an important advantage of breast MRI is that the cancer in the opposite breast can usually be detected at the time of initial diagnosis. Early detection enables both cancers to be treated at the same time, and increases the odds of a successful treatment. The study also showed that if a woman had a negative MRI for the opposite breast, she had only a very small chance of developing a second cancer later on.

“Although no imaging tool is perfect,” Lehman said, “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.”

The researchers suggest that women with a new cancer diagnosis in one breast discuss with their doctors whether to undergo an MRI of the opposite breast in addition to a rigorous clinical exam and mammography. They say the practice could lead to fewer prophylactic double mastectomies, more informed treatment decisions and greater peace of mind for women recently diagnosed with breast cancer.