A new study published by Conant et al in the journal Radiology found that the advantages of digital breast tomosynthesis over digital mammography, including increased cancer detection and fewer false-positive findings, are maintained over multiple years and rounds of screening. In addition, research showed that digital breast tomosynthesis screening helped detect a higher proportion of poor-prognosis cancers than digital mammography.

Digital breast tomosynthesis, sometimes called three-dimensional (3D) mammography, emerged in the past decade as a tool for breast cancer screening. The procedure uses an x-ray tube that moves in an arc and takes low–radiation dose projections of the breast from different angles. Varying the angle allows for multiple data points that can be reconstructed in different ways.

“Tomosynthesis allows viewing of the breast in multiple layers or slices,” said study lead author Emily F. Conant, MD, Professor and Chief of Breast Imaging in the Department of Radiology at Perelman School of Medicine at the University of Pennsylvania in Philadelphia. “This ability to scroll through slices of otherwise overlapping breast tissue helps us not only detect more cancers but also better characterize benign or normal areas of the breast.”

Background and Methods

Numerous studies have shown that digital breast tomosynthesis is superior to digital mammography for cancer detection and reducing recall rates. However, most of the published data on digital breast tomosynthesis screening have been from first round of screening—an instance when cancer detection rates and recall rates are expected to be higher than with subsequent rounds of screening. Less is known about the performance of digital breast tomosynthesis over time.

For this study, the research team looked at outcomes for patients over a 5-year period after they began imaging all their screening patients with digital breast tomosynthesis in the fall of 2011. The study set included more than 56,000 digital breast tomosynthesis exams, along with 10,500 prior digital mammography exams. The researchers compared imaging findings with results from local cancer registries.

Results

Cancer detection rates were 6 per 1,000 for digital breast tomosynthesis, compared with 5.1 per 1,000 for digital mammography alone. Screening recall rates were 8% for digital breast tomosynthesis, compared with 10.4% for digital mammography alone. The numbers held steady across all 5 years of tomosynthesis screening. Almost a third of cancers detected with digital breast tomosynthesis were associated with a poorer prognosis, compared with a quarter of those detected with digital mammography alone.

“We showed that the improved performance with digital breast tomosynthesis was maintained over multiple years,” said Dr. Conant. “This is the longest follow-up with cancer registry matching that has been published thus far.”

Dr. Conant attributed the improved outcomes achieved with tomosynthesis to better visualization of both benign and malignant lesions and a reduction in tissue superimposition.

“With tomosynthesis, you can remove some of the overlapping or obscuring breast tissue so that both normal and abnormal findings are better seen,” she said. “That provides both improved cancer detection and decreased false-positives.”

One of the key strengths of the study was its reliance on a diverse population of women. For instance, African American women, who are known to develop more aggressive breast cancer subtypes at an earlier age, made up about half of the study group.

“We found different types of biology in the cancers detected across our diverse population, and that's an important takeaway of this paper,” said Dr. Conant. “Our results show that we can improve our screening outcomes for younger women with digital breast tomosynthesis by finding clinically important cancers earlier, with fewer false-positives.”

While more studies with diverse populations and long-term follow-up are needed, the initial findings underscore the strength of tomosynthesis in breast cancer screening. “This is very promising and important data that certainly can be used to model larger trials,” concluded Dr. Conant.

Disclosure: For full disclosures of the study authors, visit pubs.rsna.org.