Breast MRI found to result in more biopsies than mammography

The use of magnetic resonance imaging brings many benefits to cancer care, but the imaging modality appears to prompt more biopsies than are necessary.

A recent study found that breast cancer patients who were screened with MRIs underwent twice as many biopsies as those that were screened with mammography alone.

The research, published in the journal Radiology, contends that the extra screening with MRI technology is not necessarily an improvement over what would have been detected with the typical use of mammography.

In fact, the authors say there were no differences between surveillance MRI and mammography in the ability to distinguish breast cancer from other findings, or to rule out cancer.

After women complete treatment for breast cancer, guidelines recommend annual breast screening, traditionally including mammography, to screen for re-emergence of the cancer. In recent years, breast MRI increasingly is being used to screen women who have had breast cancer, often between yearly mammograms, says Karen Wernli, an associate investigator at Kaiser Permanente Washington Research Institute and an affiliate professor of health services at the University of Washington School of Public Health.

Unlike previous studies, this one adjusted for differences between women who only received mammography and women who received breast MRI in addition to mammography. The women who received breast MRI tended to have a more advanced stage of cancer, denser breasts and diagnosis at a younger age, which can all raise the risk of second cancers.

"This might be one reason for the slightly higher cancer rate the study found with the addition of breast MRI," Wernli says. "Further, women who had more education and income were also more likely to receive breast MRI—not specifically because they had higher risk of second cancers, but because they likely had more access to resources."

Supplementing mammography with breast MRI is recommended for women at high risk for breast cancer (such as those with certain mutations and family histories). In 2018, the American College of Radiology recommended yearly breast MRI also for breast cancer survivors who either have dense breasts or had breast cancer diagnosed before age 50. This study focused on the use of breast MRI only in women with prior breast cancer.

This is the largest and most comprehensive study of its kind to date, including more than 13,000 women age 18 or older diagnosed with stage 0 to III breast cancer. They were screened with nearly 34,000 mammograms and more than 2,500 breast MRIs from 2005 to 2012. The study used data from five registries in the Breast Cancer Surveillance Consortium (BCSC)--The Carolina Mammography Registry, Kaiser Permanente Washington, New Hampshire Mammography Network, San Francisco Mammography Registry and Vermont Breast Cancer Surveillance System.

"Evidence about breast MRI's benefits and harms in breast cancer survivors is lacking," said Karla Kerlikowske, MD, a professor of medicine and of epidemiology and biostatistics at the University of California, San Francisco and Veterans Affairs. "This study helps fill that gap. And women with prior breast cancer need to remember to continue with annual mammography."