Magnetic resonance imaging helps detect breast cancer but does not eliminate need for biopsy

A multicenter study of 821 patients referred for breast biopsy based on prior examinations that suggested cancer finds that while magnetic resonance imaging (MRI) distinguishes between benign and malignant breast tumors better than mammography, biopsies are still needed to confirm the diagnosis.

The study, called the International Breast MR Consortium, was carried out in 14 university hospitals in the United States and Europe, including Johns Hopkins, from June 1998 through October 2001. All patients underwent MRI exams prior to breast biopsy.

David Bluemke, M.D., Ph.D., associate professor of radiology at the Johns Hopkins University School of Medicine, led the Hopkins team that examined 200 of the 821 patients enrolled in the study and reviewed data from all study participants. MRI correctly detected cancer in 356 of 404 cancer cases, resulting in a sensitivity of 88.1%. It correctly identified as negative for cancer 281 of 417 cases without cancer, producing a specificity rate of 67.7%, compared to 52.8% for mammography.

While MRI was good at finding cancer, it was less effective in ruling out malignancies, Bluemke says. “People who have an abnormal mammogram need to have biopsies of suspicious lesions,” he says. “While MRI aids in determining the extent of the cancer, it is not a substitute for breast biopsy. Importantly, however, the MRI was not adversely affected by factors such as breast density, tumor type or menopausal status, which frequently complicates mammographic interpretations.”

Bluemky believes MRI will be most beneficial for patients with difficult to interpret mammograms.