Magnetic resonance imaging (MRI) is more accurate for detecting breast cancer than mammography, ultrasound, or clinical breast examination alone in women with BRCA1 or BRCA2 mutation, according to a study in the September 15th issue of the Journal of the American Medical Association.

Women with BRCA1 and BRCA2 mutations who do not undergo prophylactic surgery have a lifetime risk of breast cancer of up to 85 percent, with a significantly higher risk of breast cancer than the general population from age 25 years onward, according to background information in the article. Current US recommendations for women who have a BRCA1 or BRCA2 mutation are to undergo breast surveillance from age 25 years onward with mammography annually and clinical breast examination every 6 months; however, even with this regimen many tumors are detected at a relatively advanced stage.

It has been thought magnetic resonance imaging, ultrasound, or both might improve the ability to detect breast cancer at an early stage. In the current work, Ellen Warner, MD, and her Canadian colleagues compared the sensitivity and specificity of four methods of breast cancer surveillance (mammography, ultrasound, MRI, and clinical breast exam) in women with BRCA1 or BRCA2 mutation.

The study included 236 women aged 25 to 65 years with BRCA1 or BRCA2 mutations who underwent 1 to 3 annual screening examinations consisting of MRI, mammography, and ultrasound at a teaching hospital between November 1997 and March 2003. On the day of imaging and at 6-month intervals, clinical breast examination was performed.

During the study period, 22 cancers were detected (16 invasive carcinomas and 6 ductal carcinoma in situ). Of these, 17 (77 percent) were detected by MRI versus 8 (36 percent) by mammography, 7 (33 percent) by ultrasound, and 2 (9.1 percent) by clinical breast examination. All 4 screening modalities combined had a sensitivity of 95 percent versus 45 percent for mammography and clinical breast exam combined.

“This study of 236 BRCA1 and BRCA2 mutation carriers demonstrates that the addition of annual MRI and ultrasound to mammography and clinical breast examination significantly improves the sensitivity of surveillance for detecting early breast cancers,” the authors wrote. “… Our results support the position that MRI-based screening is likely to become the cornerstone of breast cancer surveillance for BRCA1 and BRCA2 mutation carriers, but it is necessary to demonstrate that this surveillance tool lowers breast cancer mortality before it can be recommended for general use.”

In an accompanying editorial, Mark E. Robson, MD, and Kenneth Offit, MD, MPH, wrote that Warner et al have clearly documented the risks and benefits of breast MRI screening in women at the highest levels of hereditary risk.

“Their findings, in combination with those of another recent study, strongly suggest that women with BRCA mutations should be offered such screening. Women and their physicians must, however, be aware that both sensitivity and specificity of screening MRI may be substantially less than described if different imaging protocols are followed or if experienced radiologists and suitable technology, including the capability to perform magnetic resonance-guided biopsies, are not available.

“A technology assessment by one large insurance carrier has already supported the rationale for MRI screening of BRCA mutation carriers and other women at high hereditary risk for breast cancer, even in the absence of a randomized controlled trial demonstrating a mortality benefit. Remaining questions, largely centered on specificity, recall rate, and positive predictive value, argue against routine application of MRI screening for women at lesser degrees of risk without carefully designed studies, preferably randomized controlled trials, delineating test performance in those specific populations,” the authors concluded.