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Screening BRCA Carriers for Breast Cancer

In this study, MRI was the most sensitive modality for making the diagnosis in young women at high risk.

Women with BRCA1 and BRCA2 gene mutations should be screened aggressively if they do not undergo prophylactic mastectomy. To determine the relative value of several screening modalities, Canadian researchers screened 236 BRCA carriers (mean age, 47) with gadolinium-enhanced magnetic resonance imaging (MRI), ultrasound, mammography, and clinical breast examination, all on the same day; 58% underwent a second round of screening 1 year later, and 36% underwent a third round. Protocols for further evaluation of screening abnormalities were specified in advance.

Overall, 22 cancers were diagnosed (21 detected by at least one screening modality; 1 detected between screenings). Sensitivities for detecting these 22 cancers were 77% for MRI, 36% for mammography, 33% for ultrasound, and 9% for clinical exam. Seven cancers were detected by MRI alone, 2 by mammography alone, 2 by ultrasound alone, and none by clinical exam alone. The higher sensitivity of MRI came at the expense of lower specificity and more false positives than with mammography; positive predictive values (proportions of positives that were true positives) were 46% for MRI, 41% for ultrasound, and 89% for mammography.

Comment: Results from this study and another recent study (Journal Watch Aug 10 2004) show that MRI is more sensitive than are other modalities for diagnosing breast cancer in young women at high risk. Although the lower specificity of MRI leads to more biopsies of benign lesions, most high-risk women likely would accept this tradeoff. The optimal combination of screening tests for BRCA carriers, the performance of MRI in non-research settings, and the effect of MRI on reducing breast cancer mortality all require further study.

— Allan S. Brett, MD

Published in Journal Watch General Medicine October 5, 2004

Citation(s):

Warner E et al. Surveillance of BRCA1 and BRCA2 mutation carriers with magnetic resonance imaging, ultrasound, mammography, and clinical breast examination. JAMA 2004 Sep 15; 292:1317-25.

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