MR more than doubles breast cancer detection among high-risk patients

Combining x-ray mammography with breast MR can double the number of breast cancers found among women at high risk for the disease, according to a report issued July 2 by the ECRI Institute. The use of MR as an adjunct, however, will cause the number of false positives to rise, said ECRI, an independent nonprofit health services research agency that reviews medical devices, drugs, biotechnologies, procedures, and health services.

Dr. Carol Lee, chair of the Commission on Breast Imaging at the American College of Radiology, reviewed the ECRI results and said the organization also endorses the American Cancer Society's recommendation that screening MRI be performed on women at very high risk for breast cancer.

"Although it has not yet been shown that mortality from breast cancer is reduced by the addition of MRI to mammography for screening the high-risk population, a growing body of evidence demonstrates that MR can detect cancers in these women that are not detected by mammography or physical examination," Lee said.

The ECRI report is based on an analysis of data from six studies that screened 1920 women thought to have a 30% or higher risk of developing breast cancer due to family history. Women ranged from 38 to 46 years old when the 3770 screening exams were performed. Each year, the participants were screened using MR, x-ray mammography, ultrasound, and breast examination.

The addition of MR made finding true positives 2.7 times more likely than when x-ray mammography alone was used. Alluding to the diagnostic power of MR, finding true positives was 2.3 times more likely when women were screened with only this modality.

While screening with MR plus x-ray mammography finds more cancers, the combination also leads to more false-positive results, according to the report. For every 10 additional cancers detected by MR, another 16 false positives will appear, but the number is not unusual.

"Whenever you increase the cancer detection rate, you have to expect some additional false positives," said Wendy Bruening, a senior research analyst at ECRI Institute and lead author of the study.

Among high-risk patients, a higher rate of false positives may be acceptable, Bruening said. One reason is that breast cancer in high-risk women can be more aggressive.

"For women at high risk of cancer, the benefit of finding more cancers earlier may outweigh the harm of unnecessary testing," she said.