Digital Tomosynthesis vs Mammography in Unmasking Breast Cancer
Elizabeth A. Morris, MD, FACR
DIGITAL TOMOSYNTHESIS is rapidly replacing full-field digital mammography, because “it allows a more efficient diagnostic workflow and leads to a more confident interpretation,” according to Elizabeth A. Morris, MD, FACR, Chief of the Breast Imaging Service, Memorial Sloan Kettering Cancer Center, New York. At the 2017 Miami Breast Cancer Conference, Dr. Morris explained why this new modality may be superior to digital mammography for detecting early breast cancer.1
“The benefits of digital imaging over film screen have been numerous…. But disappointingly, digital mammography has not improved the cancer detection rate in women to the extent that was hoped, although it has shown a modest improvement in women with dense breasts,” Dr. Morris said. For one reason, there is still superimposition of normal tissue, which can obscure masses or malignancy when two-dimensional imaging is used on three-dimensional structures, she explained.
Digital technology allowed the development of digital breast tomosynthesis, an advanced application that is informally called “3D [three-dimensional] mammography” (in contrast to conventional 2D digital mammography). “Digital breast tomosynthesis has arrived on the world stage in time to address many of the limitations of mammography,” she said. “Digital tomosynthesis is a new, better mammogram; has improved screening metrics; and is rapidly becoming the screening modality of choice.”
Breast Density, Invasive Cancers
DENSE BREASTS are problematic in screening. They “not only mask cancer…but they also confer an increased risk for developing breast cancer”—one that is about four to six times that of a woman without dense breasts, according to Dr. Morris. As breast density increases, so does the rate of interval cancers. Breast density, in fact, is the most prevalent risk factor for breast cancer in both pre- and postmenopausal women, “so it is something we do need to pay attention to,” she urged.
Digital breast tomosynthesis is able to unmask cancers that are masked by mammography as a result of overlapping tissue. With a better ability to recognize false-positives, recall rates are less with the newer technology.
In addition, digital breast tomosynthesis better detects invasive cancers. In a 2014 study, Friedewald et al found that when tomosynthesis was used in addition to digital mammography, 29% more breast cancers were detected, 41% more invasive cancers were detected, and call-backs for false-positives occurred 15% less often.2
“The conclusion is that digital breast tomosynthesis finds more of the invasive, harmful cancers and saves women the anxiety and cost of having additional screenings for what turns out to be a false alarm,” Dr. Morris continued.
After 4 years of screening via digital breast tomosynthesis in that study, the cancer detection rate remained high and the recall rate remained lower, indicating sustainability of this approach. She added: “What we really need to see is the interval cancer rate. It seems to be trending down…. We would like to see it trend down more, because if the interval cancer rate goes down, that means we are picking up the cancers we need to be picking up.”
More Efficient Workflow
THE EFFICIENCY OF THE WORKUP of suspicious breast lesions is also enhanced with the use of tomosynthesis, she continued. “The diagnostic evaluation is much better and the workflow is improved where we decrease additional mammographic use and may go straight to ultrasound, which the patient likes,” she noted.
There is a reimbursement code for digital breast tomosynthesis, but reimbursement varies by state, with five states currently mandating insurance coverage. Medicare reimburses for digital breast tomosynthesis at a rate of $50 more than that for a standard mammogram, indicated Dr. Morris. ■
DISCLOSURE: Dr. Morris reported no conflicts of interest.
1. Morris E: Is tomosynthesis mammography ready for prime time? Invited Lecture. 2017 Miami Breast Cancer Conference. Presented March 10, 2017.
2. Friedewald SM, Rafferty EA, Rose SL, et al: Breast cancer screening using tomosynthesis in combination with digital mammography. JAMA 311:2499- 2507, 2014.