AMSTERDAM, Netherlands—3D mammography (tomosynthesis) is the optimal practical alternative for adjunctive breast screening in women whose standard 2D mammograms are negative but who have dense breasts, according to findings reported at the European Breast Cancer Conference from the Adjunct Screening with Tomosynthesis Or Ultrasound in women with mammography-Negative Dense breasts (ASTOUND) study (Abstract 3LBA).
“Tomosynthesis detected an additional four breast cancers per 1,000 women screened,” said Nehmat Houssami, MBBS, MPH, MEd, PhD, Professor of Public Health at the University of Sydney, Australia. And although seven per 1,000 were detected by ultrasound, Houssami said ultrasound breast screening was impractical for widespread use. “The exciting thing for us is that tomosynthesis may be a far more pragmatic way of screening women with dense breasts,” she told OT.
In a press briefing, Houssami said: “These findings will have immediate implications for both screening practice and for guiding new research in dense breasts.” And she added that until now there had been no prospective trial comparing the addition of ultrasound or tomosynthesis to standard mammograms in these women.
Interim analysis of 3,231 asymptomatic women with mammography-negative screens and dense breasts examined with both tomosynthesis and ultrasound—under the leadership of Alberto Tagliafico MD, Radiologist and Assistant Professor of Human Anatomy at the University of Genoa in Italy—found 24 additional breast cancers: 13 by tomosynthesis and 23 by ultrasound.
But concern was voiced here about whether the additional cancers detected had any implications for long-term outcomes. Commenting on the study at a news briefing Emiel J. T. Rutgers, MD, PhD, Surgical Oncologist, Head of Department at the Netherlands Cancer Institute, Amsterdam, acknowledged the ASTOUND trial demonstrated that adding 3D mammography or ultrasound can detect more cancers than standard mammography.
“But my worry is that they found many more lesions, which were suspected to be cancer but weren't. So I'm not completely sure that this is the solution for women with dense breasts in itself,” he said in an interview with OT.
Houssami told OT, however, that the main implication of the ASTOUND study was to raise awareness that it's not practical to use ultrasound to screen dense breasts, but that 3D mammography is—and that it could be integrated as part of the standard screen. And she suggested that “density tailored screening” be investigated in new studies for women with dense breast tissue.
“We might also be able to get evidence about whether using this approach not only finds more cancers but will reduce the rate of missed cancers when these women are followed up,” she said.
Also, she explained the 3D mammogram could be integrated as part of a standard screen, with 2D images generated from the same tomographic data so separate mammograms would not be needed. And Houssami said that, since tomosynthesis detected more than half of the additional breast cancers, the implication was that it could potentially be the primary mammography screening method so adjunct imaging would not be needed.
Rutgers regarded the standard mammogram as the “least worst we have!” And he said it was necessary to rely on it, because whole population 2D digital screening had already been shown to reduce breast cancer mortality.
“And I'm absolutely not sure that increasing anxiety in one in five women by telling them they have dense breasts and actually screening is useful,” he told OT.
Neither was he in favor of taking legal steps—as in some U.S. states—to assess breast density routinely and inform women about it “when there isn't an answer to that challenge.”
Chair of the European Breast Cancer Conference Fatima Cardoso, Director of the Breast Unit at the Champalimaud Clinical Center, Lisbon, Portugal, said ASTOUND provides important evidence of the potential benefit of ultrasound or tomosynthesis for screening women as the first prospective trial comparing additional screening in women with dense breasts. “[But] issues of cost-effectiveness must be addressed before we can change current screening practices,” she said.
Houssami acknowledged she didn't have the final answer on how adjunct screening affects health outcomes. “But we are optimistic that, as we move into the future, women with dense breasts may be guided to having the 3D mammogram rather than the 2D screening mammogram—which is just not finding all the cancers,” she said.
But she agreed that it is not yet known whether adjunct screening improves screening efficacy and brings benefit beyond standard mammography—taking into account the additional false positives as well. “So our study does not provide all the answers on this issue but provides the first critical piece of information on how these two tests compare,” she said.
And Houssami pointed out that, if a woman is concerned that her breasts are very dense on the mammogram, the data from ASTOUND are now available to help the discussion about her choice of whether to add ultrasound or tomosynthesis screening. “I would discuss with her the pros and cons of adding another test to improve sensitivity for detecting cancer, but would also point out this could have additional harms such as more false alarms,” she said.
Peter Goodwin is a contributing writer.