How DBT is impacting BI-RADS assessments: 4 key takeaways

58-year-old woman with invasive ductal carcinoma (arrows) detected on screening mammography and digital breast tomosynthesis (DBT). Source: American Journal of Roentgenology

Over time, the addition of digital breast tomosynthesis (DBT) has been found to have a significant impact on a case’s Breast Imaging Reporting and Data System (BI-RADS) final assessment, according to a recent study published in Radiology.

Madhavi Raghu, MD, Yale University School of Medicine, and colleagues conducted a retrospective study of diagnostic mammograms at a single academic study one year before implementation of DBT and three years after implementation.

Overall, the team found that “the potential effect of tomosynthesis in the diagnostic setting is promising,” noting several trends that were noticeable as DBT became more common at the facility over time.

1. More exams were classified as BI-RADS categories 1 & 2

The data revealed a large increase in the proportion of studies classified as BI-RADS categories 1 or 2 (“benign”) after the facility switched from 2D mammography to DBT. Those categories made up more than 58 percent of all exams in the year before DBT implementation (“the 2D mammography group”), and that number jumped to more than 75 percent of all exams by the third year after DBT implementation (“the DBT year 3 group”).

2. Less exams were classified as BI-RADS category 3

In addition, the proportion of lesions classified as BI-RADS category 3 (“probably benign”) decreased from more than 33 percent in the 2D mammography group to more than 16 percent in the DBT year 3 group.

Raghu et al. noted that this result of implementing DBT could lead to less anxious patients and potential increases in cost savings.

“Categorization of a finding as probably benign commits the patient to close mammographic follow-up, which can be inconvenient for patients, increases anxiety, and increases health care costs as compared with BI-RADS 1 and 2 classifications,” the authors wrote. “Therefore, it is desirable that we decrease the rate of BI-RADS 3 assessments while maintaining acceptable cancer detection rates.”

“No significant change” was found in the rate of exams classified as BI-RADS categories 4 and 5, the authors wrote.

3. There was a significant increase in PPV 3

Raghu and colleagues noted an increase of 69 percent in positive predictive value after biopsy (PPV 3). PPV was more than 29 percent for the 2D mammography group and 50 percent in the DBT year 3 group.

“The PPV 3 in our study increased, without a notable change in the proportion of biopsy recommendations, thereby reducing the false-positive rate associated with breast biopsies,” the authors wrote.

The authors also observed that PPV increased each year after DBT implementation, hitting 41 percent in the first year, 45 percent in the second year, and then that previously-mentioned figure of 50 percent in year 3.

4. Less malignancies were categorized as calcifications

While more than 28 percent of malignancies were categorized as calcifications in the 2D mammography group, that number was down to 16 percent in the DBT year 3 group.

“A greater proportion of malignancies were described as noncalcified lesions, particularly masses and architectural distortions,” the authors wrote. “Mass margins are more confidently analyzed with tomosynthesis compared with conventional mammography, allowing for better distinction of malignant and benign lesions. These findings are similar to those of other recent studies that have demonstrated increased diagnostic accuracy for noncalcified lesions, including masses and architectural distortions, with tomosynthesis.”

The authors said their study did have limitations. For instance, MR utilization was not evaluated at the study, and there is the possibility that factors unrelated to DBT implementation may have played some role in the observed changes.