Mammograms In 3-D May Be Better, But Hard Proof Is Missing
A newer form of mammogram may do a better job of finding cancer, a study finds. But the technology is still too untested to know if it's going to be useful for most women or even to know for sure who might benefit.
It's called breast tomosynthesis, or 3-D mammography. Since being approved by the Food and Drug Administration in 2011, the new type of scan has been touted by radiologists.
"I strongly encourage you to take advantage of this technology for your mammogram today," says the website of a radiology practice in Washington, D.C. "3-D mammography is helping us every day to find more early curable breast cancers."
But so far there has not a lot of evidence to back up the claim of superiority. As a result, many insurers aren't paying for it. If a woman wants a 3-D mammogram, she'll probably have to pay $50 or $100 out of pocket to have the extra scan added to a conventional mammogram. And she'll get an extra dose of radiation in the process.
Adding the 3-D technique increased the cancer detection rate from 4.28 to 5.24 per 1,000 patients, according to data presented Tuesday at the Radiological Society of North America meeting in Chicago. And it reduced false positives from 10.40 percent to 8.78 percent, according to Dr. Emily Conant, a professor of radiology at the University of Pennsylvania Medical Center who led the study.
"It really addresses a lot of the criticism of screening mammography by the U.S. Preventive Services Task Force and others," Conant tells Shots. In 2009, that panel recommended that women under age 50 not get mammograms because of the high rate of false alarms. The decision was denounced by many in the cancer and women's health communities.
Conventional mammograms are far from perfect, missing about 20 percent of breast cancers, according to the National Cancer Institute. Mammograms also deliver a false positive result about 10 percent of the time, which means women have to undergo more testing and the anxiety that goes with it.
Conant's team looked at results from 15,633 women who had 3-D scans at Penn in 2011. That year, the hospital started using the technology on every woman who walked in the door for a mammogram. They then compared the findings with results for 10,752 women who'd had standard digital mammograms at the hospital the year before.
It wasn't a randomized trial. And the results could be better because the first time a new test is used it typically picks up cancers that were missed by the old technology. After that, the success rate often drops.
Still, Conant is enthusiastic. "It's an exciting platform," she says. "I would highly recommend seeking out tomosynthesis."
Other breast imaging experts aren't so sure. "The gains seem to be modest in both directions," says Dr. Carol Lee, a diagnostic radiologist at Memorial Sloan-Kettering Cancer Center. "Is this something that will prove to be worth the additional time, expense and radiation exposure? I think that Dr. Conant's study is encouraging, but it's not the definitive study."
"We need to wait and see if the next round shows the same benefit, and whether we can figure out if it's for everybody, every year," says Dr. Barbara Monsees, a professor of radiology at the Washington University School of Medicine in St. Louis.
There's been speculation that women with dense breasts may benefit more from 3-D mammograms because the usual mammogram isn't good at seeing through dense tissue.
Standard mammograms take two images of each breast, one vertical and one horizontal. In a 3-D mammogram, the X-ray machine swings in an arc to take about 60 1-millimeter-thick images. The radiologist then views them like a digital flipbook. That should up the odds of spotting tiny tumors.
But there are as yet no data showing 3-D really is better for dense breasts or whether some other subgroup of women might benefit more from this technology. "I think it will get worked out eventually," Monsees tells Shots.
Right now, women have to get both a regular mammogram and the 3-D version, which means they get a double dose of radiation. That's still within safe limits, Conant says, though not ideal.
Update 11:58 a.m.: The FDA approved an application from Hologic, Inc., manufacturer of a 3-D scanner, for a software module to make 2-D images from a 3-D scan. This would reduce women's radiation exposure.
Tomosynthesis "is not the be-all and end-all," Conant agrees. Instead, she hopes it's the beginning of an evolution toward more precise, personalized breast cancer screening.
In November, the Centers for Medicare and Medicaid Services posted an FAQ stating that breast tomosynthesis should be included in the cost of regular mammography for Medicare patients, which may pressure private insurers to start paying for it. But that won't necessarily make women's decisions any easier.
"I can't give you a, 'Yes, you should, no, you shouldn't,' " Lee says of whether women should go 3-D at this point.
When she started doing mammography 30 years ago, Lee says, there were no other choices. Now women can choose sonograms, MRIs and various flavors of X-ray screens. "Unfortunately, the more tools we get, the harder it is to know which ones to use."
Copyright 2020 NPR. To see more, visit https://www.npr.org.