Reuters Health Medical News
June 25, 2014
Combining digital mammography with a 3-D technique may improve identification of breast cancers and decrease the need for additional testing, according to a new study.
"We're detecting more invasive cancers while calling fewer women back for additional imaging," said Dr. Sarah Friedewald, the study's lead author. "It's a more accurate exam."
Friedewald is co-medical director at the Caldwell Breast Center at Advocate Lutheran General Hospital in Park Ridge, IL.
Instead of creating a two-dimensional image as with digital mammography, tomosynthesis creates a three-dimensional image that allows examination of breast tissue from multiple angles.
"It's a more accurate picture of what's going on with the breast," Friedewald said.
Digital mammography has been criticized because it does not always spot cancerous tumors and sometimes identifies noncancerous masses in the breast, the researchers write in JAMA, the journal of the American Medical Association.
The U.S. Food and Drug Administration approved tomosynthesis to be used in combination with digital mammography in 2011. It requires a modified mammography machine and roughly doubles the dose of radiation.
"Most patients won't notice a difference," Friedewald said. "They're still placed and compressed. The machine still looks like a standard mammogram."
Previous studies looking at mammography plus tomosynthesis have found benefit, but those studies tended to be from individual hospitals in the U.S. and Europe.
For the new study, the researchers used data from 13 hospitals to compare outcomes for women who were screened for breast cancer during the year before tomosynthesis was introduced at each center to outcomes for those screened after the technique was put in place.
Overall, they had information on 281,187 breast exams without tomosynthesis and 173,663 with it.
After the 3-D technique was added, 16 fewer women were asked back for additional screening per 1,000 breast exams.
Women who had breast exams with tomosynthesis were more likely to get biopsies, but those biopsies were more likely to be positive.
Roughly one extra cancer was detected for every 1,000 breast exams done using tomosynthesis, the researchers calculated.
"I think this is enough to show that 3-D (imaging) is better than 2-D (imaging), but we didn't address the questions of who, when and how often patients should be getting mammograms," Friedewald said. "In terms of that debate, we didn't set out to answer those questions."
As for whether women should seek out breast screening that uses tomosynthesis, Dr. Etta Pisano from the Medical University of South Carolina (MUSC) in Charleston and Martin Yaffe from the University of Toronto write in an editorial accompanying the new study that it's still uncertain.
"For those who interpret the evidence to suggest that screening saves lives without undue false-positive results and overdiagnoses, this study contributes to the case for tomosynthesis over digital mammography," they write.
For those who question whether mammography is useful, they say the study may not be enough to change opinions.
Pisano, who is dean of the College of Medicine at MUSC, said she'd like to see more information on an even newer tomosynthesis system that involves less radiation. That system uses a synthetic two-dimensional image.
"I would like to see some data on that system before people rush out and get (tomosynthesis)," Pisano said.
She added that newer technologies are not always better, compared to older technologies that may cost less.
A digital mammogram costs between $200 and $300, but is covered by insurance for most women without a co-pay. The addition of tomosynthesis can add an extra $100 or more to the bill, which is not typically covered by insurance.
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