By Andrew M. Seaman
NEW YORK (Reuters Health) - More and more American women are undergoing breast magnetic resonance imaging to screen for cancer, according to two new studies.
There are still concerns, however, that expensive MRIs are not being used among the groups of women who would benefit most from the tests.
"It's a great new test but no one had looked at how and if it was really used," Natasha Stout, who led one of the new studies, said. "These are the first studies to really document the use and rates of use for breast MRIs."
Stout is an assistant professor in the Department of Population Medicine at the Harvard Medical School and Harvard Pilgrim Health Care Institute in Boston.
In addition to not exposing women to radiation, Dr. Shelley Hwang said MRIs are known to be more sensitive and show more small abnormalities than traditional mammograms. But that also means more false alarms that result in biopsies.
Hwang, chief of breast surgery at Duke University in Durham, North Carolina, co-wrote an editorial accompanying the new studies in JAMA Internal Medicine.
Both the American Cancer Society and the National Comprehensive Cancer Network recommend breast MRIs be used in conjunction with mammograms among women with a lifetime breast cancer risk of 20 percent or higher, usually due to their family history.
Stout's team analyzed MRI trends at two healthcare systems in the northeastern U.S. from 2000 through 2011. The group had data from 10,518 women 20 years old and older who had at least one breast MRI.
Another group, led by Karen Wernli at Group Health Research Institute in Seattle, used data from five U.S. breast cancer registries from 2005 through 2009. Those included information on 8,931 breast MRIs and about 1.3 million mammograms performed on women between 18 and 79 years old.
Both teams found that breast MRIs have become more common.
Stout and her colleagues found an increase from less than one breast MRI for every 1,000 women in 2000 to 10 breast MRIs per 1,000 women in 2011.
Wernli's team found the use of breast MRIs increased from about four per 1,000 women in 2005 to 12 per 1,000 women in 2009.
"The main motivation behind this study has been that while there has been an increased use of breast MRI, no one has been able to determine why there was an increase in breast MRI use," Wernli said.
What her group found was that about 40 percent of breast MRIs were being used to help make a diagnosis following another test or observation. About 32 percent were used for screening.
Wernli's team also found the proportion of MRI-screened women who met the cutoff for a high risk of breast cancer increased during the study. Still, only 5 percent of high-risk women were screened with MRI and they made up just one-quarter of women who were screened that way.
Hwang and her co-author Dr. Isabelle Bedrosian from the MD Anderson Cancer Center in Houston wrote that the data "indicate the need for better patient selection for breast MRI screening."
Both studies showed the use of breast MRIs leveled out after 2008.
Hwang told Reuters Health this may show that doctors were quick to adopt the new technology but then pulled back on its use once organizations put out their recommendations.
"It wasn't really until the guidelines came along when people started dialing back on using them in the less beneficial situations," she said, adding that more research is underway to see if breast MRIs are also beneficial in diagnosing breast cancers.
Stout told Reuters Health it will be important to continue looking at how many women are receiving breast MRIs and why.
"I think monitoring this going forward is important to make sure we're using this expensive technology wisely," she said.
Hwang said a mammogram traditionally costs about $300. But a breast MRI can cost between $700 and $1,200, depending on where women live.
She also said doctors can use simple online calculators to determine a woman's risk of breast cancer to show who would benefit most from breast MRIs.
SOURCES: http://bit.ly/17lsadg, http://bit.ly/17lseK9 and http://bit.ly/17lshFK JAMA Internal Medicine, online November 18, 2013.