April 3 (Bloomberg) -- Magnetic resonance imaging tests added to annual mammograms and ultrasound caught 56 percent more breast cancers in a study that suggests the extra scan may improve detection for women at increased risk for the disease.
Adding just an ultrasound to a mammogram caught 29 percent more cancers than mammogram alone among women with a higher cancer risk or dense breast tissue, a risk factor, according to the study published in the Journal of the American Medical Association. The added tests, though, also boosted false positive results, which can lead to unnecessary biopsies.
The findings add to a 2008 study by study author Wendie Berg that found that ultrasound plus mammograms helped detect more breast cancers than mammograms alone and confirm that women with dense breast tissue along with another risk factor, such as family history of the disease, can benefit from the added test. MRIs, though, should be reserved for those at the highest risk because of cost and high false positive rates, Berg said.
“For women who have dense breasts, adding ultrasound to mammography will increase the chance of finding invasive breast cancer before it spreads to the lymph nodes,” said Berg, a professor of radiology at the University of Pittsburgh School of Medicine, in a statement. “MRI detected additional invasive cancers not seen on mammography or ultrasound. However, we found that MRI was significantly less tolerable than mammography or ultrasound for many study participants.”
Of participants offered an MRI, only 58 percent accepted, Berg said.
Cancer Society Recommendations
The American Cancer Society recommends that women age 40 and over get a mammogram every year. The group recommends high-risk women have a mammogram in combination with magnetic resonance imaging to boost their chances of early detection. The U.S. Preventive Services Task Force though said in 2009 that most women ages 40 to 49 don’t need mammograms, restricting the test to those with a disease history or who had a greater risk for another factor.
Ultrasound imaging uses high-frequency sound waves to produce pictures of the internal structure of the breast in real time. The mammogram, in contrast, x-rays the breast, while MRI scans create a three dimensional image of the breast using magnetic fields, showing where tissue density varies and where growth of blood vessels may feed tiny tumors too small to feel with the hand or see on a mammogram.
The researchers in the study included 2,662 women at increased risk of breast cancer who had three annual mammograms plus ultrasound and 612 who agreed to undergo an MRI after all three mammograms and ultrasounds were completed. They found 111 breast cancers. Of those, 33 were found by mammography and another 32 by the addition of ultrasound, for an added annual cancer detection rate of 3.7 cancers per 1,000 screens. MRI detected an additional 9 cancers, at a rate of 14.7 cancers per 1,000 screens.
Berg said these findings show that adding ultrasound improves the effectiveness of the screening for those women who are at higher risk for the disease and for those at the highest risk who are unable to have a MRI.
“While supplemental ultrasound and MRI screening detect more cancers, it is important to emphasize that an annual mammogram is still recommended and neither ultrasound nor MRI is meant to replace mammography,” said study author Ellen Mendelson, a professor of radiology at Northwestern University’s Feinberg School of Medicine, in Chicago, in a statement.
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