Breast cancer screening with digital breast tomosynthesis (DBT), also known as "3D mammography," resulted in a 6.7% lower chance of a false positive result than standard digital mammography—however, half of women will still experience a false positive result over a decade of annual screening, according to a new study published Friday in JAMA Network Open.

Study details and key findings

For the study, researchers analyzed data from screening examinations conducted at 126 radiology facilities in the Breast Cancer Surveillance Consortium from January 2005 to December 2018. Their analysis included 903,495 women between the ages of 40 and 79, with an average age of 57.6 years. Throughout the study, participants received nearly 3 million screening examinations.

Of the exams included in the study, 71.8% were annual screening mammograms, 16.8% were biennial screening mammograms, and 11.4% were triennial or longer screenings. In total, 15% of the exams were conducted with DBT.

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

With biennial screening, researchers found that the risk of at least one false positive recall over 10 years was significantly lower, no matter the screening modality. The cumulative recall rate for DBT was 35.7% compared with 38.1% for digital mammography with biennial screening.

Notably, the probability of cumulative false positive recall decreased with increasing age—with the highest cumulative rates occurring in women ages 40 to 49 undergoing annual screening.

In addition, the probability of a false positive recall also declined with decreasing breast density—with estimated probabilities of a false positive recall after 10 years of 67.3% among women with very dense breasts, and 31% among women with entirely fatty breasts.

Ultimately, with annual screening, the 10-year cumulative probability of experiencing at least one false positive recall was 6.7% lower for DBT than standard digital mammography, according to Diana Miglioretti, a lead author of the study and division chief of biostatistics at University of California, Davis's department of public health sciences.

Still, 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," said Lydia Pace of Brigham and Women's Hospital.

While the comparable reduction may seem "modest," Miglioretti and her colleagues wrote in the study, the 6.7% reduction alone "equates to many thousands of individuals in absolute numbers, especially for annual screening, which is the dominant practice in the U.S."

"Whenever you're called back for an additional workup, it's very stressful because women think they may have cancer," said Miglioretti.

"Often it may take days to even weeks to get that resolved," she added. "The main thing is we want to alleviate women's anxiety over these false positives and understand they are very common."

Commentary

False positives have been a longstanding problem. However, "3D mammography" has been promoted by hospitals, doctors, and some patient groups for its ability to provide better images—and previous studies have similarly suggested DBT results in fewer false positives, Axios reports.

In a commentary of the study, Pace noted that although false positives are associated with heightened anxiety, inconvenience, and expense, "more information is needed to understand the association of DBT with overdiagnosis, which is the more clinically important harm of screening."

Currently, Miglioretti's team is studying the risk factors associated with getting called back for additional imaging.

"If we can identify women, like younger women, women with dense breasts at higher risk of being recalled, we can have the radiologist read the mammogram while she waits so that she can get any additional workup that day. That greatly reduces women's anxiety because they don't get this call saying, 'We need you to come in for additional imaging,'" Miglioretti said.

Ultimately, Pace noted that the study serves as a reminder that even in practices that routinely use DBT, physicians should always warn patients that false positive results are a possibility. (Bassett, MedPage Today, 3/25; Reed, Axios, 3/25;  Ho et al., JAMA Network Open, 3/25)