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Over the past decade, women of color and those with lower income or education levels were less likely to receive digital breast tomosynthesis (DBT) screening than white women and the more educated and affluent, though the gap has narrowed over time.

In a retrospective study involving over 2 million breast cancer screening exams across five U.S. states, the proportion of DBT screening use increased from 3.3% in 2011 to 82.6% in 2017, reported Christoph Lee, MD, MS, of the University of Washington School of Medicine in Seattle, and colleagues, writing in .

"This study was about whether adoption of this technology is equitable. We're showing that it has not been, even though it has been FDA-approved for a decade now," Lee said in a . "Black and Hispanic women, and less-educated and lower-income women have not been able to obtain 3D mammography as easily as white, well-educated, and higher-income women."

When looking at facilities offering both 3D and standard digital mammography at the time of a screening exam, 53.1% of white women were able to receive the more advanced screening option over the study period, followed by 44.0% of Hispanic women, 42.8% of Asian women, and 37.7% of Black women.

Women without a high school diploma were less likely to receive DBT than those with a college degree at these dual-modality facilities (40.8% vs 50.6%, respectively), as were women living in the lowest-income neighborhoods (43.9% vs 51.4% for the highest income).

"We're going in the wrong direction," said Lee. "You have a lot more women in certain subpopulations benefiting from new technologies and other subpopulations not. Existing disparities in breast cancer screening outcomes could widen unless these factors are addressed."

DBT, or 3D mammography, was first approved by the FDA in 2011. Research has suggested that the technology is associated with lower recall rates than standard 2D digital mammography, and guidelines recommend DBT as the preferred option for breast cancer screening.

But the technology is more costly and while most screening sites in the U.S. offer DBT on at least one of their mammography machines, this still only accounts for roughly 40% of all certified units, according to the study.

"DBT costs more than 2D because it generates digital 'slices' of breast tissue, which take more time to acquire and to interpret," Lee noted, adding that depending on state laws and factors with insurance, patients may have to pay out of pocket for the difference in price.

The retrospective study looked at 2,313,118 screening exams in the Breast Cancer Surveillance Consortium, which were conducted from 2011 to 2017 at 92 imaging facilities in California, Illinois, New Hampshire, North Carolina, and Vermont. Nearly two-thirds of the sample were white, while 13.1% were Black, 11.6% Asian, and 6.5% were Hispanic. Just under half had a college degree, 22.4% had some college, 19.4% had a high school diploma, and 8.7% did not graduate high school.

Across all facilities, white women were most likely to undergo screening at a center offering DBT (37.2%) over the study period, followed by Black women (34.4%), Hispanic women (30.6%), and Asian women (16.5%).

On multivariate analysis, access to DBT by race or ethnicity was starkest early on after DBT was introduced in 2011. After 1 year of adoption, Black women were least likely to undergo screening at a facility offering DBT compared with whites (relative risk 0.05, 95% CI 0.03-0.11), followed by Asian (RR 0.28, 95% CI 0.11-0.75) and Hispanic (RR 0.38, 95% CI 0.18-0.80) women.

Compared with college graduates, lower education level was also tied to lower DBT access after a year of adoption (2012): no high school diploma (RR 0.18, 95% CI 0.10-0.32), high school graduate (RR 0.62, 95% CI 0.42-0.91), some college (RR 0.71, 95% CI 0.57-0.89).

In 2017, however, access to a facility offering DBT was not significantly tied to either education or race/ethnicity, but actual use of the technology remained lower among Asian women, those without a high school diploma, and those residing in "small rural settings."

In all, 41 of the facilities offered both technologies at the time of a screening exam, with DBT use increasing from 32.7% after a year of adoption to 87.7% within 5 years at these dual-modality sites. After a year of adoption, Black women (RR 0.83, 95% CI 0.82-0.85) and Hispanic women (RR 0.87, 95% CI 0.85-0.89) were less likely to receive DBT screening compared with whites screened at the same facility. Four years after DBT adoption, this disparity remained only among Black women (RR 0.92, 95% CI 0.90-0.94).

Similarly, women without a high school diploma were less likely to receive DBT compared with those with a college degree at dual-modality facilities, with risk ratios ranging from 0.79 (95% CI 0.74-0.84) to 0.88 (95% CI, 0.85-0.91) across the study period. Women in the lowest quartile of median income were also less likely to receive DBT compared to those in the highest quartile, with risk ratios ranging from 0.89 (95% CI 0.87-0.91) to 0.99 (95% CI 0.98-1.00).

A significant limitation to the study was that Lee and colleagues could not determine women's insurance status, which was likely an important factor in DBT access, the group acknowledged. They also noted that Medicare did not cover DBT until 2015.

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