MR assumes high profile in breast imaging

Proponents of breast MR were vindicated this week by a surge of supporting data, spearheaded by American Cancer Society guidelines that captured the top spot on network news. The guidelines advise the use of this modality on women at high risk of developing breast cancer.

The clinical value of breast MR was most evident, however, in data published March 29 in The New England Journal of Medicine that documented the effectiveness of MR in finding diseased tissue missed by other screening efforts.

Up to 10% of women newly diagnosed with cancer in one breast develop cancer in the opposite breast, yet early signs of this contralateral cancer often are not found with mammography, according to Dr. Etta Pisano, a principal investigator and Kenan professor of radiology and biomedical engineering at the University of North Carolina School of Medicine at Chapel Hill. They are, however, evident on MR, as demonstrated in a clinical trial involving UNC and 24 other clinical sites in North America.

"This study is pretty definitive evidence that the opposite breast needs to be evaluated with MRI," said Pisano, who coauthored the NEJM paper.

The evidence backing Pisano's claim arose from a trial conducted by the American College of Radiology Imaging Network and funded by the National Cancer Institute. Last week, luminaries from major universities warned Congress that cuts in National Institutes of Health funding threaten to impede critical biomedical research (Lack of NIH funding threatens future progress, SCAN 3/28/07).

Results from the NIH-supported MR trial indicate that for women already diagnosed with cancer in one breast, MR detects more than 90% of cancers in the opposite, or contralateral, breast. MR detected cancer in the opposite breast in 30 of 969 women who had recently been diagnosed with cancer in only one breast. The cancers in the opposite breast were missed by previously conducted mammography and clinical exams.

The research raises the profile of breast MR as a tool in the fight against breast cancer, but its impact will be limited. The researchers recommend MRI screening only for women already proven to have the disease or those who have a family history of breast cancer.

"MR screening is very expensive and should be used judiciously for high-risk populations," Pisano said. "The last thing we would want is for every woman to think she should get an MRI."