"Ours is the first large-scale report of how women are actually using breast MRI in national community practice," said lead author Karen Wernli, PhD, an assistant investigator at Group Health Research Institute. This community-based reporting is made possible by the Breast Cancer Surveillance Consortium (BCSC), the nation's largest and most comprehensive collection of information on screening for breast cancer, funded by the National Cancer Institute (NCI).
Breast MRI is recommended in addition to X-ray mammography to screen women at high (20-25 percent or more) risk for developing breast cancer during their lifetime. And among women in the study screened with breast MRI, the proportion at high lifetime risk for breast cancer rose from 9 percent in 2005 to 29 percent in 2009.
"We found that use of breast MRI for breast cancer screening—rather than diagnosis—is rising, as is appropriate," said Dr. Wernli, who is also an affiliate assistant professor of health services at the University of Washington School of Public Health. During the study period, the proportion of breast MRIs used for diagnosis fell, and the proportion used for screening rose. Screening is done routinely in the absence of suspicion, and diagnostic evaluation is the workup after other breast imaging, like mammography or ultrasound. Diagnostic evaluation with breast MRI, in particular to avoid a biopsy, is not recommended before breast cancer is diagnosed. After a diagnosis, some people use breast MRI to evaluate for staging and extent of disease.
Despite their disparate methods and populations, both papers in the same issue of the journal report similar findings: Breast MRI is now being used for screening more often than for diagnosis; and its use for screening is more common in average-risk women than in higher-risk women—but that pattern is improving.
"Our study suggests breast MRI is being used better," Dr. Wernli said. But it also shows that more improvement is needed to use breast MRI more appropriately for risk-based screening: The vast majority of the women at high lifetime risk for breast cancer—who could most likely benefit from breast MRI—appeared not to be using it yet, instead using only mammography for screening. Meanwhile, many women at average risk for breast cancer were screened using breast MRI, even though mammography is still considered the best screening test for them.
"To prevent the underuse by women at high risk, and overuse by those at average risk," Dr. Wernli said, "we need to strengthen the network of providers, like genetic counselors, who can provide women with the breast cancer risk counseling that they need."
Dr. Wernli explained: "We took a snapshot of how doctors are interpreting the guidelines and using this new technology." The study of more than 6,700 women receiving breast MRI is among the first to measure why women receive this test.
The researchers used a pool of data on women aged 18 years from five community-based BCSC registries—Group Health, North Carolina, New Hampshire, San Francisco, and Vermont—using electronic data systems, billing codes, and radiology reports. Women completed a questionnaire about their age, ethnicity, family history of breast cancer, history of breast procedures, and other information.