The new X-ray technology, called tomosynthesis, was approved in 2011 and is still considered experimental by insurers, who do not cover it.
Nonetheless, 3D is catching on. The study, published in Wednesday's
The findings bolster smaller studies that also have found tomosynthesis to be a breakthrough.
"Do I think 3D is ready for prime time? I really do," said senior author
"I definitely believe tomosynthesis is going to become the standard of care," said lead author
In an editorial, two radiology researchers were more cautious, calling the results "promising."
Tomosynthesis (tomo is Greek for "slice") acquires a set of images from an X-ray tube that sweeps over the breast. A computer algorithm instantly creates a 3D reconstruction.
A machine equipped with tomosynthesis can perform 2D, or 3D, or both during a single breast compression, so the patient perceives no difference. Combining 2D and 3D doubles the radiation dose, but it remains below safety limits. Last year, the
Tomosynthesis addresses mammography's primary limitation: When the breast is squashed, overlapping tissue can hide tiny malignancies while making normal structures appear suspicious.
"With 2D, you mostly see the covers of the book," Conant analogized. "With 3D, you can leaf through and see the pages."
The study -- funded by
The biopsy rate increased slightly, but women who underwent biopsy because of suspicious 3D images were more likely to have cancer.
Adding 3D did not increase detection of cancer confined to the milk ducts, ductal carcinoma in situ. Ductal malignancies, which account for almost a quarter of new cancer diagnoses, present a dilemma because doctors can't predict which ones will never invade surrounding tissue. Thus, these preinvasive cancers are treated -- critics would say overtreated -- with surgery, radiation, and, often, hormone therapy.
"The important thing about 3D is that we weren't detecting more of the 'in situ' cancers," Conant said. "What we were really impacting is invasive cancer."
"It was very deep and very early" stage, said Forman, who had a lumpectomy and radiation. "My father was an oncologist at
The study does not shed light on the ultimate value of screening for a disease that kills 40,000 U.S. women annually. Previous research found screening reduces breast cancer-related deaths by up to 50 percent, but expert organizations continue to debate whether to start mammography at age 40 and how often to do it.
Adding to the angst, numerous states, including
"The study didn't set out to address the controversy over who should be screened or when or how often," Friedewald said. "It was just trying to show tomosynthesis is a better mammogram. I think that finding is definitive."
It remains to be seen how quickly insurers agree. Some centers (not
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