Assessing mammographic density change within individuals across screening rounds using deep learning-based software

The purposes are to evaluate the change in mammographic density within individuals across screening rounds using automatic density software, to evaluate whether a change in breast density is associated with a future breast cancer diagnosis, and to provide insight into breast density evolution.

Mammographic breast density was analyzed in women screened in Malmö, Sweden, between 2010 and 2015 who had undergone at least two consecutive screening rounds $<30$ months apart. The volumetric and area-based densities were measured with deep learning-based software and fully automated software, respectively. The change in volumetric breast density percentage (VBD%) between two consecutive screening examinations was determined. Multiple linear regression was used to investigate the association between VBD% change in percentage points and future breast cancer, as well as the initial VBD%, adjusting for age group and the time between examinations. Examinations with potential positioning issues were removed in a sensitivity analysis.

In 26,056 included women, the mean VBD% decreased from 10.7% [95% confidence interval (CI) 10.6 to 10.8] to 10.3% (95% CI: 10.2 to 10.3) ( $p<0.001$ ) between the two examinations. The decline in VBD% was more pronounced in women with initially denser breasts (adjusted $\beta =-0.10$ , $p<0.001$ ) and less pronounced in women with a future breast cancer diagnosis (adjusted $\beta =0.16$ , $p=0.02$ ).

The demonstrated density changes over time support the potential of using breast density change in risk assessment tools and provide insights for future risk-based screening.