The American Cancer Society, Susan G. Komen and the U.S. Preventive Services Task Force also say there isn’t yet enough evidence to advise women on 3D mammograms.
When the Food and Drug Administration approved the first 3D mammography system, made by Hologic, the agency required the technology to be safe and effective at finding breast cancer – not at improving survival.
“The companies do the minimal research needed to get FDA approval, and that usually means no meaningful evidence of how it helps patients,” said Diana Zuckerman, president of the National Center for Health Research.
Valenti said Hologic presented strong evidence to the FDA. “The data was overwhelming that 3D was a superior mammogram,” Valenti said.
Describing a breast exam as 3D may conjure up images of holograms or virtual reality. In fact, tomosynthesis is closer to a mini-CT scan.
Although all mammograms use X-rays, conventional 2D screenings provide two views of each breast, one from top to bottom and one from the side. 3D screenings take pictures from multiple angles, producing dozens or hundreds of images, and take only a few seconds longer.
Yet some studies suggest that 3D mammograms are less accurate than 2D.
A 2016 study in The Lancet Oncology found that women screened with 3D mammograms had more false alarms. A randomized trial of 29,000 women published in The Lancet in June showed that 3D detected no more breast tumors than 2D mammograms did.
And, like all mammograms, the 3D version carries risks. Older 3D systems expose women to twice as much radiation as a 2D mammogram, although those levels are still considered safe, said Diana Miglioretti, a biostatistics professor at the University of California-Davis School of Medicine.
Valenti said the newest 3D systems provide about the same radiation dose as 2D.
Diagnosing more cancers doesn’t necessarily help women, Brawley said. That’s because not all breast tumors are life-threatening; some grow so slowly that women would live just as long if they ignored them – or never even knew they were there. Finding these tumors often leads women to undergo treatments they don’t need.
A 2017 study estimated 1 in 3 women with breast cancer detected by a mammogram are treated unnecessarily. It’s possible 3D mammograms make that problem worse, by finding even more small, slow-growing breast tumors than 2D, said Dr. Alex Krist, vice chairman of the U.S. Preventive Services Task Force, an expert panel that issues health advice. By steering women toward 3D mammograms before all the evidence is in, “we could potentially hurt women,” Krist said.
Some experts worry that patients, who tend to overestimate their risk of dying from breast cancer, are acting out of fear when they choose treatment.
“If there was ever an audience susceptible to direct-to-consumer advertising, it’s women afraid of breast cancer,” Zuckerman said.
Some proponents of 3D mammograms imply that women who opt for 2D are taking a risk.
The first question many women have about 3D mammograms is: Are they less painful?
In ads, Hologic claims its 3D device was less painful for 93% of women. But that claim comes from a company-funded study that hasn’t been formally reviewed by outside experts, Zuckerman noted. Given the limited data provided in the study, it’s possible the findings were the result of chance, said Zuckerman, who called the ads “very misleading.”
Valenti said peer review is important in studies about cancer detection or false alarms. But when it relates to “general patient satisfaction or patient preference, those are data that we get in other ways,” he said. “Plenty of [doctors] have the [3D] system now and you can get feedback from them. “
While screenings may not generate a lot of income, they can attract patients who need other, more profitable hospital procedures.
“Anytime you diagnose more tumors, you can treat more tumors,” said Amitabh Chandra, director of health policy research at Harvard University’s John F. Kennedy School of Government.