There has been a lot of buzz recently about three-dimensional mammography, otherwise known as tomosynthesis.
While screening mammography is proven to decrease breast cancer deaths, it is far from perfect. Out of every 1,000 mammograms performed, approximately 100 women will need additional testing. Most of these women do not have cancer. When they are called back, most of them will need only one or two more special view mammograms or an ultrasound to prove they do not have cancer. About 20 out of these 100 will need a biopsy, and only 4 or 5 will ultimately prove to have cancer. The 95 patients out of the original 1,000 who were called back, but did not prove to have cancer, are called “false positives.”
A second problem with screening mammography is that it does not detect all cancers, especially in patients with dense breasts. In addition to mammography, some other optional tests may be recommended to detect more cancers, such as ultrasound or MRI. Additional testing will find more breast cancers, but all testing – until now – adds to the burden of false positives. It seems there is no free lunch: If you increase your ability to detect more cancers, the price you pay will be more false positives.
Tomosynthesis is different. This is the first technique that is able to both improve cancer detection AND reduce false positives.
Watch this video to see how tomosynthesis works and what you may expect as a patient.
Although tomosynthesis is relatively new (it was approved for use in the US in 2011), it has been used in Europe for a number of years. There is already mounting evidence showing its ability to detect small, invasive cancers not seen with two-dimensional mammography as well as its ability to reduce false positives. A recent widely-publicized, 13-institution study conducted in the US showed the same results.
Small invasive cancers are the kind we want to detect with screening mammography. When these cancers are identified early and treated early, we are able to make the most impact on a patient’s changes of survival. At the UVM Medical Center, we have used tomosynthesis in clinical practice – both for screening and diagnostic mammography – since 2012. Our experience has matched that in previously reported studies. Our rates of callbacks from screening have decreased approximately 25 percent since before we began using tomosynthesis. This decrease is even more marked for women undergoing their first, or baseline, mammogram. Our cancer detection rate for small invasive cancers has significantly increased, while our detection rate for non-invasive cancer (DCIS) has not changed. When a patient is called back from a screening 3D mammogram, most of the time we can go straight to ultrasound; bypassing the need for additional mammographic views. This saves time, money, and radiation dose.
Tomosynthesis or 3D mammography improves our ability to detect cancers (although it still may not detect all cancers, particularly in dense breasts) and results in a decreased chance of false positives as compared with 2D mammography. It is the only technique right now to accomplish both – and give your radiologist even more confidence in his or her diagnosis.
Patients should be aware that there are some disadvantages: It does take longer for your radiologist to interpret a 3D mammogram. While Medicare has agreed to pay for this service since January 2015, as of April 2015, most commercial payers have not. Because we currently perform 2D mammography in addition to 3D mammography (2D is currently still required, as it gives an overall view and allows comparison with prior studies), the radiation is nearly twice as much. This is still below FDA limits and less than the radiation used when we performed mammograms on x-ray film, before the advance of digital technology. (This difference in radiation is akin to the difference between living in Vermont at sea level and living in Denver at higher altitude.) A new software technique is now available that will be able to synthesize a 2D picture from a 3D view, thus requiring no extra radiation over conventional 2D digital mammography. We hope to get this in the future so we may perform 3D mammography on all women without any increased radiation.
Learn more about Breast Imaging at the University of Vermont Medical Center. 3D mammography is available at all three of our campuses. Please contact us at firstname.lastname@example.org if you have questions about tomosynthesis or breast imaging.
Sally Herschorn, MD, radiologist, is Medical Director of Breast Imaging at the University of Vermont Medical Center.