For Young Women Undergoing MRI Mammography Is of No Added Value

According to a recent prospective multicenter cohort study, a revision of current recommendations for breast cancer screening is advisable at least for young women carrying an increased risk of breast cancer. The results of the EVA trial confirm that magnetic resonance imaging (MRI) is substantially more accurate for early diagnosis of breast cancer than digital mammography or breast ultrasound: MRI is three times more sensitive for breast cancer than digital mammography.

For the EVA (Evista Alendronate Comparison) trial, nearly 700 women were enrolled. The goal of the trial was to refine existing guidelines for surveillance of women at high and moderately increased risk of breast cancer. Findings suggest that in these women, MRI is essential for early diagnosis and that a mammogram or an ultrasound examination does not increase the "cancer yield” compared to what is achieved by MRI alone. The researchers concluded that an annual MRI is not only necessary, but also sufficient for screening young women at elevated risk of breast cancer. In women undergoing screening MRI, mammograms will have no benefit and they should be discontinued. Moreover, MRI screening is important not only for women at high risk, but also for those at moderately increased risk.

Between 2002 and 2007, the EVA trial recruited 687 women who carried a moderately increased risk of breast cancer (lifetime risk of 20% and over). Women underwent 1679 screening rounds consisting of annual MRI, annual digital mammography, and half-annual screening ultrasound examinations. During this period, 27 women received a new diagnosis of invasive cancer or ductal carcinoma in situ (DCIS).

Of all imaging methods under investigation (digital mammography, ultrasound, and MRI), MRI offered by far the highest sensitivity: MRI identified 93% of breast cancers. Thirty-seven percent of cancers were detected by ultrasound. The lowest sensitivity was achieved by digital mammography, which identified only one-third of breast cancers (33%). These results confirm once more that MRI is essential for surveillance not only of women at high risk, but also for women at moderately increased risk of breast cancer. Moreover, the results contradict current guidelines according to which mammography is considered indispensable for breast cancer screening.

One aim of the EVA trial was to question this concept and to ask whether it is still appropriate to require that MRI should only be used in addition to mammography. The results, according to the researchers, speak for themselves: If an MRI is available, then the added value of mammography is literally negligible. The investigators concluded that MRI is necessary as well as sufficient for screening young women at elevated risk of breast cancer. Since mammography appears to be unnecessary in women undergoing MRI, its use is no longer justifiable, and current guidelines should be revised to reflect this.

Current guidelines for women at high familial risk of breast cancer recommend a yearly MRI scan (with or without ultrasound) and annual MRI scan starting at age 25-30. "These guidelines were set up based on little or no scientific evidence, and mainly reflect expert opinion,” summarized Prof. Christiane Kuhl, a radiologist at the University of Bonn (Germany) and lead investigator of the EVA trial. "In the light of the results of the EVA trial, such recommendations should be revisited.”

This seems even more important because digital mammography uses X-rays (ionizing radiation) to detect breast cancer. "The radiation dose associated with regular mammographic screening is clearly acceptable and safe,” underscored Dr. Kuhl. "However, regular mammographic screening usually starts at age 40-50.” The situation is different if systematic annual mammographic screening is started at age 25-30. "Not only because these women will undergo more mammograms and therefore will experience a cumulative lifetime radiation dose that will be substantially higher, but also because the breast tissue of young women is more vulnerable to the mutagenic effects of radiation.”

This appears to be particularly true for BRCA mutation carriers. "Accordingly, we impose more radiation on less radiation-tolerant breast tissue for a very limited, if any, diagnostic benefit,” noted Dr. Kuhl. Therefore, he advocates a revision of existing guidelines: "It is no longer justifiable to insist on annual mammographic screening women in their thirties if they have access to screening MRI.”

In the past, MRI was used strictly in addition to mammography only. The allegedly high rate of false-positive diagnoses and the allegedly insufficient sensitivity for DCIS were the main reason to discourage its use as a stand-alone method for breast cancer screening. "In this multicenter trial, with basic quality assurance implemented not only for mammography, but also for MRI, we were able to prove that false-positive diagnoses are avoidable if MRI studies are interpreted with adequate radiologist expertise.”

In the EVA cohort, the positive predictive value achieved with MRI was already even higher than that of mammography or breast ultrasound. "Moreover, we found that MRI offered the highest sensitivity especially for DCIS,” added Dr. Kuhl. "It is simply wrong to state that we need a mammogram to detect intraductal cancer.”

The study's findings were published in the February 22, 2010, issue of the Journal of Clinical Oncology.

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