MRI Beats Mammography or Ultrasound at Detecting Breast Cancer

July 31, 2007

SEATTLE -- Screening MRI had a higher rate of breast cancer detection than either mammography or ultrasound screening in high-risk women, but it nearly quadrupled the biopsy rate, researchers here found.

SEATTLE, July 31 -- Screening MRI had a higher rate of breast cancer detection than either mammography or ultrasound screening in high-risk women, but it nearly quadrupled the biopsy rate, researchers here found.

The diagnostic yield was 3.5% with MRI, 1.2% with mammography, and 0.6% on ultrasound, reported Constance D. Lehman, M.D., Ph.D., of the University of Washington, in the August issue of Radiology.

"Although the specificity of MRI was lower than that of mammography or clinical breast examination (89.8%, 95.0%, and 98.1%, respectively), the overall accuracy of MRI was significantly higher," wrote Dr. Lehman and colleagues.

In their multi-center study, investigators compared the three screening modalities in 171 asymptomatic women who were confirmed carriers of a BRCA1 and/or BRA2 mutation or had at least a 20% chance of carrying the mutation.

The women were screened for breast cancer with MRI, mammography, and ultrasound, with no more than 90 days between each screening test.

A total of 16 biopsies were performed and six cancers were detected in the cohort, for a cancer detection rate of 3.5%.

All six cancers were detected on MRI, two were detected on screening mammography, and one on screening ultrasound.

MRI findings led to biopsy in 8.2% of cases; mammography and ultrasound each led to biopsy in 2.3% of cases.

The positive predictive value of MRI was 43%, with mammography it was 50%, and with ultrasound it was 25%.

Ultrasound did not identify any of the four cancers missed on screening mammography.

Dr. Lehman and associates concluded that their study further supports MRI "as an important complement to mammography in screening women at high risk for breast cancer."

They acknowledged, however, that their study was small, did only a single round of screening, and did not include long-term follow-up.

At this time, they noted, "further studies are needed to more clearly address the potential role of ultrasound in this patient population before it can be promoted as a reasonable alternative to MRI for screening women at high risk."