Third study finds MRI superior to mammography.(Gynecology)

ORLANDO -- A British study has found magnetic resonance imaging to be nearly twice as sensitive as x-ray mammography for detecting breast cancers in young women at high risk for disease due to genetic mutations or other family history of breast disease.

The finding does not resolve concerns about cost, however.

In a review of the study at the annual meeting of the American Society of Clinical Oncology, Kelly K. Hunt, M.D., calculated that magnetic resonance imaging (MRI) would find six breast cancers in 100 patients screened. "The positive predictive value being only 6%, can we really afford this?" asked Dr. Hunt of the M.D. Anderson Cancer Center in Houston.

The Magnetic Resonance Imaging for Breast Screening (MARIBS) researchers reported their conclusions simultaneously at the meeting and in The Lancet (2005;365:1769-78). Theirs is the third published study to support MRI in young high-risk women with dense breast tissue that tend to obscure tumors on mammograms (N. Engl. J. Med. 2004;351:427-37 and JAMA 2004;292:1317-25).

All told, 35 breast cancers were found in 649 women who underwent a screening round of MRI and mammography. These cancers included 19 breast cancers detected by MRI alone and 6 by mammography alone. Only eight were detected by the two screening methods, and two were missed by both.

Investigator Martin O. Leach, Ph.D., calculated that MRI detected 77% of breast tumors, and mammography detected 40%. Combining the two technologies produced a sensitivity of 94%, which Dr. Leach of the Institute of Cancer Research in London described as "very reasonable."

While MRI detected tumors in all risk groups enrolled in the study, it was dramatically more effective than mammography in those women who were carrying the BRCA 1 mutation. Dr. Leach reported MRI sensitivity among BRCA 1 carriers to be 92% vs. 23% with mammography.