Ultrasound plus mammography, performed annually for three years, spotted about 30% more cancers than mammography alone, says Wendie A. Berg, MD, PhD, of American Radiology Services at Johns Hopkins-Green Spring Station in Lutherville, Md.
"Importantly, most of the cancers that we found with ultrasound were the small invasive cancers that are likely to spread and could ultimately kill a person," she tells WebMD.
The study of more than 2,800 women was presented at the annual meeting of the Radiological Society of North America.
3 Years of Breast Screening Help
The research builds on a 2008 study, also led by Berg, that showed that a single screen with ultrasound and mammography improves the detection of early breast cancers over a mammogram alone in women at increased risk for breast cancer.
The new study sought to determine if detection could be further improved by performing annual screens with both tools for three years.
"One of the issues that had never been looked at was whether we had to do ultrasound every year or whether you would catch them the first time you looked," Berg says.
The new study showed "that we could increase detection significantly with each annual screening, so it does help to do ultrasound each year in addition to the mammogram," she says.
Annual Ultrasounds Improve Breast Cancer Detection
Dense breast tissue is not only a known risk factor for breast cancer, but also makes it harder to spot cancer on mammograms.
About a third of the mammograms that were done the first year were digital; this increased to 52% by the third year.
A total of 111 women were diagnosed with cancer over the three-year period.
Combined screening with mammography plus ultrasound found 82% of the cancers, compared with only 53% for mammography alone, Berg says.
Nine of the cancers that were not detected with combined screening were found when MRI was offered in the third year of the study.
"Having digital mammography didn't improve the detection rate [over film mammography]," Berg says.
MRI Spots Even More Breast Cancers
The researchers also used MRI to scan a subset of 612 patients in the third year of the study.
"MRI increased the cancer detection rate by another 56%," she says.
While the number of women studied with MRI was relatively small, this shows that "if you really want to find as many of the cancers as you possibly can, doing the MRI was even more sensitive, by far, than the combination of mammography and ultrasound," Berg says.
The major drawback to adding ultrasound or MRI screening was an increase in false-positives, with women having to then undergo biopsies, she says.
But Berg says modern biopsy techniques are "like going to the dentist. It's done in about 15 minutes with lidocaine."
Most women "say it's not a big deal, that they would rather be sure there's no cancer," she says.
Some women cannot tolerate MRI because it requires an injection or makes them feel claustrophobic, she says.
"Women at high risk of breast cancer should consider an MRI. If they can't tolerate it, ultrasound is now a viable alternative," Berg says.
RSNA spokesperson Joseph Tashjian, MD, president of St. Paul Radiology in Minnesota, tells WebMD that the findings show the value of additional screening tools in women at high risk of breast cancer.
Women should discuss the risks and benefits of additional screening with their doctors, he says.