Breast MRI moderately useful for detecting breast cancer

In women with breast lesions that are suspicious for cancer, based on clinical examination or mammography, performing a breast MRI has high sensitivity but only moderate specificity for detecting breast cancer, but does not necessarily eliminate the need for tissue sampling, according to a study in the December 8 issue of JAMA.

Mammography is the primary imaging modality used to detect clinically occult breast cancer, according to background information in the article. However, mammography has limitations in both sensitivity and specificity that have led to exploration of other imaging techniques. Magnetic resonance imaging (MRI) has been evaluated for breast imaging because of its value for assessing soft tissues of the body. Previous research has indicated that additional lesions seen by MRI that are not visible on the mammogram have been reported to be present in between 27 percent and 37 percent of patients. The use of MRI to evaluate women with mammographically or clinically suspicious breast lesions who are undergoing biopsy has shown high potential.

David A. Bluemke, M.D., Ph.D., of Johns Hopkins University School of Medicine, Baltimore, and colleagues conducted a study to determine the accuracy of breast MRI in conjunction with mammography for the detection of breast cancer in patients with suspicious mammographic or clinical findings. The International Breast MR Consortium was conducted at 14 university hospitals in the United States and Europe from June 2, 1998, through October 31, 2001. The study included 821 patients referred for breast biopsy based on suspicious mammographic, clinical or ultrasound findings. Patients had MRI examinations performed prior to breast biopsy; MRI results were interpreted at each site, with MRI investigators blinded to pathological results.

The researchers found that MRI correctly detected cancer in 356 of 404 cancer cases (ductal carcinoma in situ [DCIS] or invasive cancer), resulting in a sensitivity of 88.1 percent, and correctly identified as negative for cancer 281 of 417 cases without cancer, resulting in a specificity of 67.7 percent. MRI performance was not significantly affected by mammographic breast density, tumor histology, or menopausal status.

“In conclusion, MRI shows high sensitivity and moderate specificity for breast cancer. However, for lesions that are mammographically or clinically suspicious, tissue sampling of the breast may not be avoided with the use of MRI,” the authors write.