Digital breast tomosynthesis, also known as 3-D mammography, has the potential to significantly increase the cancer detection rate of mammography screening in women with dense breasts. This major new study was presented at the annual meeting of the Radiological Society of North America (RSNA) in Chicago, Illinois.

Breasts are considered dense if they have a lot of fibrous or glandular tissue but not much fatty tissue. Research has shown that dense breasts are more likely to develop cancer, a problem compounded by the fact that cancer can be difficult to detect on mammograms of dense breasts.

Other imaging modalities such as ultrasound and MRI are often used to help find cancers that cannot be seen on mammograms, but both modalities have higher rates of false-positive findings. This higher false-positive rate often results in more tests and unnecessary biopsies, making MRI and ultrasound expensive to implement in high-volume screening programs, according to study lead author Per Skaane, MD, PhD, from the Department of Radiology at Oslo University Hospital in Oslo, Norway.

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Skaane and colleagues have been studying tomosynthesis as a promising breast cancer screening option that addresses some of the limitations of mammography by providing 3-D views of the breast.

“Tomosynthesis could be regarded as an improvement of mammography and would be much easier than MRI or ultrasound to implement in organized screening programs,” Skaane said. “So the intention of our study was to see if tomosynthesis really would significantly increase the cancer detection rate in a population-based mammography screening program.”

The researchers compared cancer detection with full-field digital mammography (FFDM) versus FFDM plus digital breast tomosynthesis in 25,547 women ages 50 to 69 years. Breast density was classified based on the American College of Radiology’s Breast Imaging-Reporting and Data System (BI-RADS). The BI-RADS scale rates breast density from 1 (least dense) to 4 (most dense).

In the study, 257 malignancies were detected, including 105 with a density 2 rating and 110 with a density 3 rating. Of the 257 cancers, 211 (82%) were detected with FFDM plus tomosynthesis, a significant improvement over FFDM alone (163 cancers [63%]).

FFDM plus tomosynthesis pinpointed 80% of the 132 cancer cases in women with dense breasts, compared with only 59% for FFDM alone.

“Our findings are extremely promising, showing an overall relative increase in the cancer detection rate of about 30%,” Skaane said. “Stratifying the results on invasive cancers only, the relative increase in cancer detection was about 40%.”

Tomosynthesis not only improved the cancer detection rate in women with dense breasts, it also helped increase detection for women in the fatty breast BI-RADS categories. The addition of tomosynthesis to FFDM improved the cancer detection rate from 68% to 84% in women whose breasts had a BI-RADS density rating of 1 or 2.

“Our results show that implementation of tomosynthesis might indicate a new era in breast cancer screening,” Skaane said.