A key benefit, and potential harm, of adding MRI to breast cancer screening programs

Surveillance MRI can help imaging providers detect more breast cancers, according to a new study published in Radiology. However, it also leads to a much higher biopsy rate.

“People often think more testing is better,” lead author Karen J. Wernli, PhD, an associate investigator at the Kaiser Permanente Washington Health Research Institute in Seattle, said in a prepared statement. “That might be true for some women, but not necessarily all. It's important for clinicians and women to be aware of both the benefits and harms that can come from imaging.”

Wernli and colleagues examined data from more than 13,000 women who survived breast cancer. The women underwent 33,000 mammograms and more than 2,500 breast MRI examinations from 2005 to 2012. All patients were at least 18 years old, with a mean age of 60. Data came from five different sites from the Breast Cancer Surveillance Consortium.

Overall, breast MRI had a cancer detection rate (CDR) of 10.8 per 1,000 examinations. Mammography had a CDR of 8.2 per 1,000 examinations. Breast MRI had a biopsy rate of 10.1%, more than double that of mammography (4%).

Sensitivity and interval cancer rates were similar between the two modalities, the authors noted.

“It's really important for us to know that when we're making guideline recommendations and conclusions that we really look at the best quality of the evidence,” Wernli said in the same statement. “It's also very important to adjust for differences among women when we're trying to evaluate the addition of new imaging tests to surveillance mammography.”

The research did have certain limitations. The authors wrote that they did not track the reason patients were referred for breast MRI, for instance, and there was a “limited number of second breast cancer events” that kept them from learning more about when breast MRI may be more effective than mammography for surveillance. Learning more about this aspect of screening, the authors noted, could potentially help minimize “the effect of unnecessary benign biopsies.”