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Breast cancer screening with digital breast tomosynthesis (DBT), or "3D mammography," was associated with a lower probability of false-positive findings compared with standard digital mammography, investigators found.

Their comparative effectiveness study showed that 7.6% of DBT examinations resulted in a false-positive recall compared with 9.0% of digital examinations, while 1.8% and 2.1%, respectively, resulted in a false-positive short-interval follow-up recommendation, and 1.1% and 1.2%, respectively, resulted in a false-positive biopsy recommendation.

Ultimately, with annual screening, the 10-year cumulative probability of receiving at least one false-positive recall was 6.7% lower for tomosynthesis compared with standard mammography, reported biostatistician Diana Miglioretti, PhD, of University of California, Davis, and colleagues.

While in percentage terms these reductions are "modest," Miglioretti and her colleagues wrote in , that percentage "equates to many thousands of individuals in absolute numbers, especially for annual screening, which is the dominant practice in the U.S."

Even so, despite the lower probability of false-positives with DBT, the "growing availability of DBT does not substantially change the likelihood that women will experience a false-positive result over years of regular mammograms: with annual screening, about half of women undergoing screening with DBT will experience at least 1 false-positive recall," according to Lydia Pace, MD, MPH, of Brigham and Women's Hospital in Boston.

In a , Pace said that while false positives are associated with anxiety as well as time, inconvenience, and expense, "more information is needed to understand the association of DBT with overdiagnosis, which is the more clinically important harm of screening."

In the meantime, she wrote, the study is a reminder that even in practices that routinely offer DBT, physicians should caution patients that false-positive results are not unexpected.

Miglioretti's group analyzed data collected prospectively from screening examinations conducted from January 2005 to December 2018 at 126 radiology facilities in the Breast Cancer Surveillance Consortium. The analysis included 903,495 women (age 40 to 79, mean age 57.6) who had almost 3 million screening examinations during that time period.

Of the exams analyzed in this study, 71.8% were annual screening mammograms, 16.8% were biennial screening mammograms, and 11.4% followed triennial or longer screening. A total of 15% of examinations used DBT.

For annual screening, the 10-year cumulative probability of at least one false-positive result was lower with DBT versus digital mammography for all outcomes: 49.6% vs 56.3% for recall, 16.6% vs 17.8% for short-interval follow-up recommendation, and 11.2% vs 11.7% for biopsy recommendation.

With biennial screening, the investigators found that the risk of at least one false-positive recall over 10 years was substantially lower, regardless of screening modality.

For biennial screening, the cumulative recall rate for DBT was 35.7% compared with 38.1% for digital mammography. The cumulative probabilities did not differ significantly for short-interval follow-up recommendation (10.3% vs 10.5%) or biopsy recommendation (6.6% vs 6.7%).

Cumulative false-positive recall probabilities declined with increasing age, with the highest cumulative rates among women age 40-49 undergoing annual screening (68.0% with digital mammography and 60.8% with annual DBT) compared with women age 70-79 (47.0% with annual digital mammography and 39.8% with annual DBT).

False-positive recall probabilities also declined with decreasing breast density, with estimated probabilities of a false-positive recall after 10 years of annual screening of 67.3% for women with extremely dense breasts, and 31.0% for women with entirely fatty breasts.

Cumulative false-positive recalls were more common among women with extremely dense breasts but not significantly different between DBT and digital mammography. For example, the recall probabilities were 67.3% vs 65.0%, respectively, for women age 40-49 with annual screening, and 51.2% vs 46.1% with biennial screening in the same age group.

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