B reast cancer risk assessment has become increasingly important in personalized breast cancer screening strategies (1), and numerous studies have consistently validated the strong relationship between increased breast density and breast cancer risk (2)(3)(4). The most commonly used breast density assessment method is visual assessment wherein breast density is categorized based on the American College of Radiology Breast Imaging Reporting and Data System (BI-RADS), which is a subjective process (5). Most fully automated methods for breast density assessment, including ImageJ-based research methods (6) and the publicly available Laboratory for Individualized Breast Radiodensity Assessment (LIBRA) software tool (7,8), provide area-based density metrics from two-dimensional (2D) digital mammography (DM) images (8-11). However, DM is rapidly being replaced by digital breast tomosynthesis (DBT), approved by the United States Food and Drug Administration in 2011 (12). In many facilities, DBT technology is also used to reconstruct "synthetic 2D images," which may make conventional DM obsolete (13). Therefore, in view of the rapid clinical conversion to DBT imaging, fully automated methods to measure breast density from DBT are becoming increasingly essential.In DBT, quasi-three-dimensional breast image volumes are reconstructed from a series of low-dose, 2D raw projection images acquired across a limited angle (14). By providing a quasi-three-dimensional image set, DBT offers the ability to quantify dense breast tissue volumetrically, which in turn may allow for more accurate breast density measures and improved breast cancer risk estimations (15). Attempts have been made by Food and Drug Administration-cleared commercial software vendors, such as Background: While digital breast tomosynthesis (DBT) is rapidly replacing digital mammography (DM) in breast cancer screening, the potential of DBT density measures for breast cancer risk assessment remains largely unexplored.Purpose: To compare associations of breast density estimates from DBT and DM with breast cancer.
Materials and Methods:This retrospective case-control study used contralateral DM/DBT studies from women with unilateral breast cancer and age-and ethnicity-matched controls (September 19, 2011-January 6, 2015. Volumetric percent density (VPD%) was estimated from DBT using previously validated software. For comparison, the publicly available Laboratory for Individualized Breast Radiodensity Assessment software package, or LIBRA, was used to estimate area-based percent density (APD%) from raw and processed DM images. The commercial Quantra and Volpara software packages were applied to raw DM images to estimate VPD% with use of physics-based models. Density measures were compared by using Spearman correlation coefficients (r), and conditional logistic regression was performed to examine density associations (odds ratios [OR]) with breast cancer, adjusting for age and body mass index.Results: A total of 132 women diagnosed with breast cancer (mean age 6 standard...