A study in the August 11 issue of The Lancet concludes that screening for breast cancer with magnetic resonance imaging (MRI) could improve the ability to detect ductal carcinoma in situ (DCIS), especially high-grade DCIS. DCIS is a form of preinvasive breast cancer. High-grade DCIS grows quickly and is more likely to develop into invasive breast cancer.

Background
Mammography is the standard method for diagnosing DCIS, which accounts for 20% of diagnosed breast cancers. Left untreated, DCIS could progress over several years to a high-grade invasive breast cancer. MRI may be used for screening very high-risk women (such as those with known BRCA mutations) or to evaluate the both breasts before surgery at the time of diagnosis. Mammography works by highlighting calcium deposits (calcifications) around the DCIS lesions. MRI works by detecting areas of increased vascularization (growth of blood vessels), which is more commonly found around high-grade DCIS lesions.

The Study
In this study, researchers at the University of Bonn (Germany) offered mammography and high-resolution breast MRI to more than 7,000 women. From this group, 167 women had a confirmed diagnosis of DCIS. Researchers found that 93 (56%) of these lesions were visible on mammography and 153 (92%) lesions were found with MRI. Of the 89 lesions that were high-grade DCIS, 87 (98%) were found using MRI compared with 46 (52%) by mammography.

Additional perspective

“This is an exciting study that was first presented at the ASCO Annual Meeting this year, and it is encouraging to see these results published. However, this is not a recommendation for routine screening with MRI,” said Nancy Davidson, MD, ASCO President and Director of the Breast Cancer Program at the Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins University in Baltimore, Maryland.

When an MRI shows suspicious findings, the next step is a biopsy, and this can be difficult to do if the lesion is only visible with MRI. “Not many centers are able to perform an MRI-guided biopsy,” added Dr. Davidson.

Gabriel Hortobagyi, MD, FACP, ASCO’s Immediate Past President and Chair of the Department of Breast Medical Oncology at the University of Texas M. D. Anderson Cancer Center in Houston, agreed that the results wereencouraging, and discussed the concerns with MRI.

“First, this was a single study, and additional studies will need to be done to support these results. Second, this study was done at an academic medical center, with experts who have the equipment, extensive experience, and knowledge to accurately perform and interpret the MRI. Right now, there are no standards in the United States to ensure consistency between testing centers. Finally, the risk/benefit ratio for MRI screening needs to be established and communicated with patients. A false positive test leads to additional, invasive biopsies and other tests.”

Bottom line
“MRI is not the standard of care for diagnosing every breast cancer in the United States,” said Julie Gralow, MD, Chair, ASCO Cancer Communications Committee and Associate Professor of Medicine/Oncology at the University of Washington School of Medicine and Fred Hutchinson Cancer Research Center in Seattle. “The use of MRI screening is supported for women with a very high risk of breast cancer. The next step is to adopt standards for performing and interpreting breast MRI, including the ability to biopsy lesions seen only on MRI. Once the quality of breast MRI is established, we will be ready to implement clinical trials to determine whether screening MRI can improve survival without increasing the financial and psychological costs when compared with mammography, which is a standardized screening tool proven to reduce deaths from breast cancer.”

MRI for diagnosis of pure ductal carcinoma in situ: a prospective observational study. The Lancet, 2007; 370:485-492.

For More Information: Resources on this topic include the Cancer.Net Guide to Breast Cancer, Cancer.Net Feature: Mammography: What to Expect, and the Cancer.Net Feature: Magnetic Resonance Imaging—What to Expect.