Diagnostic Imaging
December 2002

OVERREAD

Experts question use of MRI as breast screening tool

Clinic promises women more accurate test than x-ray mammography

Flying in the face of conventional wisdom among radiologists, AmeriScan whole-body screening centers in Phoenix and San Jose, CA, are touting MR as a screening test superior to x-ray mammography for detecting breast cancer.

Several hundred women have undergone the $1700 to $2200 screening exams since the for-profit company began advertising the service in July, according to medical director Dr. Craig Bittner. The newspaper ads claim that mammography misses more breast cancer than it finds, jeopardizing the lives of thousands of women, and that traditional mammography leads to over 500,000 unnecessary and costly breast biopsies each year.

"MR mammography has nearly 100% sensitivity and about 80% specificity for breast cancer. The MR literature shows that it is a fantastic tool," Bittner said.

MRI is generally considered an adjunct to mammography, used in detection and staging of breast cancer. Studies are under way to evaluate the potential of MRI in screening populations as well.

"MRI of the breast is currently the most sensitive imaging technique available for the detection and staging of breast cancer," said Dr. Christiane K. Kuhl, section chief of women's imaging at the University of Bonn, Germany. "Several trials have proved that it helps detect more breast cancer than mammography and breast ultrasound. So if costs are no consideration, MRI may well be used for breast cancer screening."

In a study published in Radiology (2000;215(1):267-279), Kuhl and colleagues used MRI as a screening tool in 192 women at high risk for breast cancer. The researchers reported 100% sensitivity for MRI compared with 33% for mammography and 30% for ultrasound.

"Virtually all published data on MRI screening has been gathered in patient cohorts who are at increased risk for breast cancer," Kuhl said.

Further, all the data that have been acquired on MRI screening come from groups with extensive experience using MRI, Kuhl said. The experience of the physician doing the imaging can be key to assuring that the technique does not do more harm than benefit to the patient.

Bittner recruited MR mammography researcher Dr. Werner A. Kaiser, chair of the Institute of Diagnostic and Interventional Radiology at Friedrich-Schiller University in Jena, Germany, to develop AmeriScan's program. Bittner has trained and read cases under Kaiser's direction. Kaiser also spent several weeks training the technologists who perform the exam.

"There is no other group right now that should or could offer MRI as a screening technology," Bittner said at a recent conference in Washington, DC.

Several breast imaging experts, however, say there is no clinical evidence supporting the use of MRI as a breast cancer screening tool in low-risk asymptomatic women.

"It's really unproven. The vast majority of published work on MRI has been done in a diagnostic setting. Nobody in the field believes that MRI should be used for breast cancer screening right now," said Dr. Susan Orel, an associate professor of radiology at the University of Pennsylvania Health System.

Some experts do credit MRI with higher sensitivity for detecting breast cancer than mammography, but not without a few caveats.

A high false-positive rate can be a much larger problem for MRI in screening asymptomatic women who have a low probability of developing breast cancer.

A proven genetic disposition to breast cancer, a suggestive family history, and a personal history of breast cancer are all factors contributing to risk in women.

"It is open to question whether the good results that have been made with breast MRI in high-risk populations can be transferred to the non-high-risk screening situation," Kuhl said.

Another issue with MRI is its low specificity, which may lead to unnecessary biopsies.

"Many of the lesions found on MRI will not be amenable to biopsy and will lead to further follow-up imaging and cost, as well as increased anxiety to patients and their physicians," said Dr. Nola Hylton, an associate adjunct professor of radiology at the University of California, San Francisco, who has focused on breast imaging since joining UCSF's MR Science Center in 1993.

While the potential of MRI in breast cancer detection and diagnosis has created some excitement, according to Hylton, its benefit lies in its ability to find some cancers missed by x-ray mammography, such as those that may be found in women with dense breasts.

"The most important thing for women to know right now is that they absolutely should not forgo their regular screening mammograms," she said. "An MRI exam should not be used to replace a mammogram. It will miss calcifications, an important and early signal of breast cancer."

According to Bittner, his MR screening program breaks through an institutional logjam that has barred access to what he says is a diagnostically superior technology.

"When are we going to say that technological advancement is a good thing? We should be championing this, not trying to retard it," he said.