A new study has demonstrated that the advantages of digital breast tomosynthesis (DBT) compared with digital mammography (DM)—including increased cancer detection and fewer false positive findings—are maintained over multiple years and rounds of screening.

DBT, also called 3D mammography, emerged in the last decade as a method of breast cancer screening. The procedure uses an X-ray tube that takes low radiation-dose projections of the breast from different angles, allowing for multiple data points that can be reconstructed in different ways.

“As a radiologist, tomosynthesis allows viewing of the breast in multiple layers or slices,” said Emily F. Conant, MD, lead study author and professor in the Department of Radiology at Perelman School of Medicine at the University of Pennsylvania, in a press release. “The 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.”

DBT has been found to be superior to DM for cancer detection and reducing recall rate, or the rate at which women were called back for additional imaging based on suspicious initial findings. However, most of the published data on DBT screening have been from the first round of screening, an instance when cancer detection and recall rates are expected to be higher than with subsequent rounds of screening. Less is known about the performance of DBT over time.

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

Cancer detection rates were 6 per 1000 for DBT compared with 5.1 per 1000 for DM alone. Screening recall rates were 8% for DBT compared with 10.4% for DM alone. The numbers held steady across all 5 years of tomosynthesis screening. Almost one-third of cancers detected with DBT screening were associated with a poorer prognosis, compared with a quarter of those detected with DM alone.

“We showed that the improved performance with DBT was maintained over multiple years. This is the longest follow-up with cancer registry matching that has been published thus far,” said Conant, who 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. That provides both improved cancer detection and decreased false positives,” Conant said.

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

Although further research with diverse populations and long-term follow-up are needed, the initial findings underscore the strength of tomosynthesis in breast cancer screening, according to the study authors.

Reference
  1. Tomosynthesis Outperforms Digital Mammography in Five-Year Study [news release]. RSNA website. Published March 10, 2020. https://www.rsna.org/en/news/2020/March/Tomosynthesis-Versus-Digital-Mammography. Accessed March 17, 2020.