MRI Better than Ultrasound, Mammography in Identifying Breast Cancer in High-Risk Women

Investigators recently recommended that breast magnetic resonance imaging (MRI) should become a vital component of yearly breast cancer screening for high-risk women age 35 and older. Young women with a high genetic risk of breast cancer should start screening with breast MRI as young as age 25 or as early as age 20 if a family member had breast cancer before the age of 30.

Dr. Christopher Riedl, from the department of diagnostic radiology at the Medical University of Vienna (Austria) made these recommendations in March 2008 at the European Congress of Radiology (ECR), held in Vienna, Austria. He presented his study's findings that compared the accuracy of mammography, ultrasound, and breast MRI in detecting cancer in a cohort of 327 women who underwent 672 complete surveillance rounds at a single imaging center.

Between 1999 and 2007, 28 cancer lesions were identified. Of these, only breast MRI detected 12. Mammography detected 14 for a sensitivity of 50%, ultrasound detected 12 for 42.9% sensitivity, and breast MRI detected 24 for a sensitivity of 85.7%. In the 672 screening cycles, 136 suspicious findings (BI-RADS [Breast Imaging Reporting and Data System] 4 or 5) were detected, and all the lesions underwent needle-localized open breast biopsy. "We prefer to be aggressive with very high-risk patients,” Dr. Riedl said. About 80% of the lesions were benign.

Out of the women recruited between January 1999 to January 2001, 46 tested positive for the BRCA1 or BRCA2 gene. Starting January 2002, eligibility for the study was expanded to include women age 25 or older who had three or more first-degree relatives with breast cancer diagnosed before the age of 61, two relatives diagnosed before the age of 51, one relative diagnosed with breast cancer before the age of 36, or a relative diagnosed at any age with ovarian cancer. Women younger than age 25 with a relative who had cancer before that age were also eligible.

Women who had received treatment for breast or ovarian cancer were eligible to enroll after 12 months of treatment, unless they had metastatic disease. This expanded eligibility to a broader and more representative population of very high-risk women, according to Dr. Riedl.

The total population ranged in age from 22 to 80 years, with a median age of 41 years.
The women had annual mammograms, ultrasound, and breast MRI. Plans were made to schedule all three procedures on the same day. Young women were scheduled only during the second week of their menstrual cycle to lessen nonspecific, hormone-related enhancement of benign breast tissue. Women who failed to have the three procedures completed within 30 days were excluded from that specific screening cycle but their earlier and future completed screening rounds were evaluated.

During the course of the study, 27 of the 327 women were excluded during the course of the study because of bilateral mastectomy; 10 participants died, with five due to breast cancer and five to ovarian cancer. Mammograms were reviewed by a radiologist with 10 years of experience who knew of the women's risk factors. Breast MRI scans were reviewed by a different radiologist with 10 years of reading experience, and high-frequency ultrasound was done by one of two experienced radiologists. All radiologists were blinded to the results of the technique they were not interpreting.

In addition to detecting 42.9% of the cancers not seen in mammograms and ultrasound, breast MRI detected significantly more invasive and preinvasive cancers, according to Dr. Riedl. MRI alone identified five (54%) of the 11 cases of ductal carcinoma in situ. MRI was also better in diagnosing atypical ductal hyperplasia (ADH) lesions. Out of 35 of these premalignant lesions, 32 were detected by breast MRI alone; ultrasound detected two, and mammography detected nine.

The number of false-positive results was high, particularly for breast MRI. Mammography had 25 false-positives, ultrasound had 26, and MRI had 101. Dr. Riedl ascribed the high false-positive rate to the uncommonly high number of detected lesions classified as ADH. With this population, ADH detection is extremely important because it aids in further individual risk assessment, according to Dr. Riedl.

"For the population we studied, the question is not if these women will get cancer, but when,” Dr. Riedl concluded. "It is their personal choice about whether they wish to have prophylactic mastectomy, but we need to provide them with another alternative.”

Whether this population should not undergo mammography and ultrasound altogether, Dr. Riedl reported that this might be a future clinical protocol recommended for younger women at high risk of breast cancer, but at this time he could not definitively recommend it.


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