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Sept. 17, 2004 — MRI is more accurate for detecting breast cancer than mammography, ultrasound or clinical breast examination alone, in women who carry the BRCA1 or BRCA2 gene mutation, according to a study in the Sept. 15 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 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 (CBE) every 6 months; however, many tumors are detected at a relatively advanced stage. Magnetic resonance imaging (MRI) and ultrasound may improve the ability to detect breast cancer at an early stage.
Ellen Warner, M.D., of Toronto-Sunnybrook Regional Cancer Centre in Toronto, and colleagues compared the sensitivity and specificity of four methods of breast cancer surveillance (mammography, ultrasound, MRI, and CBE) in women with hereditary susceptibility to breast cancer due to a BRCA1 or BRCA2 mutation.
The study included 236 women aged 25 to 65 years with BRCA1 or BRCA2 mutations who underwent one to three 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, CBE was performed.
During the study period, there were 22 cancers detected (16 invasive and six ductal carcinoma in situ). Of these, 17 (77 percent) were detected by MRI vs. eight (36 percent) by mammography, seven (33 percent) by ultrasound, and two (9.1 percent) by CBE. All four screening modalities combined had a sensitivity of 95 percent vs. 45 percent for mammography and CBE combined.
"This study of 236 BRCA1 and BRCA2 mutation carriers demonstrates that the addition of annual MRI and ultrasound to mammography and CBE significantly improves the sensitivity of surveillance for detecting early breast cancers," the authors write. "... 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."
Editorial: Breast MRI for Women with Hereditary Cancer Risk
In an accompanying editorial, Mark E. Robson, M.D., and Kenneth Offit, M.D., M.P.H., of the Memorial Sloan-Kettering Cancer Center, New York, write 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 conclude.