New research suggests ultrasound won't cut it as a substitute adjunct study for screening women at high risk for breast cancer.
Breast MRI helps detect significantly more cancers in high-risk women than either mammography or ultrasound. It does so with acceptable biopsy and false-positive rates, according to a multicenter prospective breast screening pilot study published this month in Radiology (2007:244:381-388).
"The technology is very exciting. Now that we have evaluated it and see a benefit, we need to take the next step of providing access to MR for more women across the country," said lead author Dr. Constance Lehman, director of breast imaging at the Seattle Cancer Care Alliance, in an interview with Diagnostic Imaging.
Women who are at high risk for breast cancer and have an MR study do not benefit from having a screening ultrasound, the researchers concluded. Currently, ultrasound is more available.
"Figures are hard to come by, but in general, we find that more women are undergoing screening ultrasound rather than screening MRI. Instead of offering ultrasound as a reasonable alternative, we should instead focus on how to provide MRI to more women," Lehman said.
The new research was conducted by the International Breast MRI consortium and the Cancer Genetics Network. It involved six centers and 171 women.
On the basis of imaging results, 16 biopsies were performed that revealed six cancers. All the cancers were picked up with MR, whereas mammography only picked up two. Ultrasound detected only one in six cancers in high-risk women, resulting in the highest false-negative rate of the three modalities.
Ultrasound is notoriously operator-dependent. The authors note that the doctors involved in the study were very experienced with screening ultrasound, however, so they believe differences are very unlikely to be related to skill level.
"Again and again, single-site and multi-institution prospective studies are showing that MRI is the most sensitive tool we have in detecting breast cancer in high-risk patients," said Lehman, who is also a professor of radiology at the University of Washington School of Medicine.
Biopsy rates were higher with MR, at 8.2% compared with 2.3% for both mammography and ultrasound, but the false-positive rate was for MR relatively low. Positive predictive value for MR was 43%, compared with 50% for mammography and 25% for ultrasound.
"We were pleased to see that the risk of having a benign biopsy was lower than expected in these high-risk women," Lehman said.
Lehman acknowledges, however, that it is imperative to perform high-quality MR exams to help cut down on false positives.
In recognition of persuasive data and recommendations affirming the value of breast MRI, national insurance companies have been implementing favorable coverage policies for screening high-risk women, she said.
"What we need to do now is make sure national policies are put into place locally. We have seen a lot of variation and would like to see more consistency from state to state," Lehman said.
For more information from the diagnostic imaging archives:
Clinical support grows steadily for breast MRI
Breast MRI shows promise for population at high risk
