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Use of MRI to follow women with a previous history of breast cancer detected more cancers than mammography, but at a cost of significantly more biopsies, researchers reported.

While the cancer detection rate was higher for breast MRI compared with mammography alone (10.8 vs 8.2 per 1,000 examinations), the breast MRI biopsy rate was more than two-fold greater (10.1% vs 4.0%), according to Karen J. Wernli, PhD, of Kaiser Permanente Washington Health Research Institute in Seattle, and colleagues.

For women with a personal history of breast cancer, "the potential benefits and harms, specifically the effect of increased biopsies, should be carefully considered when incorporating breast MRI into surveillance imaging strategies," they wrote in .

National recommendations lack consensus on offering breast MRI for routine surveillance of women with a personal history of breast cancer, the authors pointed out. While the American college of Radiology recommends annual breast MRI for women with dense breasts who were first diagnosed with cancer < age 50, the evidence is limited on its benefits and harms in this population.

So radiologists aren't sure what to recommend for this population, and "you have women who've been diagnosed and treated for breast cancer, some of whom have been recommended to get breast MRI, and some of whom that haven't," Wernli told 乌鸦传媒. "So it's important to understand whether or not additional imaging with breast MRI is important in finding second breast cancers in women who have a previous breast cancer history."

To compare the performance of surveillance mammography with breast MRI, Wernli and colleagues collected and evaluated data from the Breast Cancer Surveillance Consortium cohort, which was conducted from 2005 to 2012, and included 13,266 women with a personal history of breast cancer.

Of these women, 11,745 only underwent mammography (with a total of 33,938 mammograms), while 1,521 underwent breast MRI (2,506 total examinations).

Wernli's group found that breast MRI had a higher cancer detection rate (10.8, 95% CI 6.7, 14.8) than mammography alone (8.2, 95% CI 7.3, 9.2) per 1,000 examinations, as well as a higher biopsy rate (10.1%, 95% CI 8.95, 11.3%) versus 4.0% (95% CI 3.7%, 4.2%).

In multivariable models, breast MRI was associated with higher detection (odds ratio 1.7, 95% CI 1.1, 2.7) and a greater than two-fold higher biopsy rate (OR 2.2, 95% CI 1.9, 2.7).

However, there were no significant differences in sensitivity between mammography and breast MRI for breast cancer detection (OR 1.1) or in interval cancer rates (OR 1.1).

"Therefore, the radiologic interpretation of mammography does not appear to miss more second cancer events that would become clinically detectable during the screening interval of 12 months compared with the radiologic interpretation of breast MRI," the authors concluded.

They noted that their measure of MRI breast sensitivity is lower than that observed in previous surveillance breast MRI studies, and suggested there could be several explanations for this difference.

For example, "A lot of studies of breast MRI may not find all the women who are false negative and who screen negative on MRI, and within a 12 month period are diagnosed with breast cancer. And if they missed them, this calculation would undercount that false negative number and inflate that measure of sensitivity. I think that is possibly the most likely reason," Wernli told 乌鸦传媒,

She also observed that the analyses were adjusted for patient characteristics, and pointed out that previous studies of breast MRI performance failed to take factors such as demographics and differences in primary cancer diagnosis and treatment into account.

For instance, "women who underwent breast MRI were likely to be younger, had higher stage primary cancers, and likely to have undergone chemotherapy," she said. "When we adjust for patient characteristics we see that the women who are getting breast MRI are different from women who are only getting mammography, and that these measures of sensitivity [between MRI and mammography] are not different."

"So it's really important when policymakers are thinking about new surveillance strategies that they consider how these comparisons are made, and that while it might be appropriate for some women to get a breast MRI, we must also consider how often to use mammography in finding second breast cancers," Wernli said. "Right now women are recommended to get a mammogram annually after the diagnosis of breast cancer," adding that, when looking at surveillance strategies, it may be appropriate to start thinking about shortening surveillance intervals for these women, rather than adding additional tests.

In an accompanying , Mary S. Newell, MD, of Emory University in Atlanta, cautioned that "we are obligated as good stewards of our health care system to determine what works best," and the benefits of breast screening MRI may not outweigh the risks.

She called the study "timely and important. We live in a world where breast imaging technologies ... are developed and honed at a rapid pace. These tools can help to find cancers not depicted at digital mammography, and usually at an early stage."