Do women with dense breasts have higher radiation dose during screening mammography?

Radiation dose during screening mammography is a concern among women. The purpose of this study was to evaluate the relative contribution of breast density to the radiation dose from screening mammography. This IRB approved retrospective study involved collecting patient age, weight, height, compressed breast thickness, and average glandular dose for each exposure for 434 sequential patients undergoing screening mammography at our institution. Automated volumetric density software was used to quantify breast density. The relationship of predictors was evaluated by univariate and multivariate analysis. Median patient age was 58 years and median body mass index (BMI) was 26.8. Median volumetric breast density was 5.8% (range 1.7-30.5%). Median compressed breast thickness was 63.4 mm (range 24.5-111.5 mm). Univariate analysis showed positive associations between radiation dose and both breast thickness and BMI, an inverse association with age, and no association with density. Multivariate regression analysis demonstrated a significant association between dose and age (P=.021), laterality (P<.001), BMI (P=.038), density (P<.001), and breast thickness (P<.001). Decomposition of the multivariate regression model coefficient of determination showed that breast thickness was the primary determinant of dose, accounting for 76% of the 58% of the dose variability, followed by density (8%), laterality (4%), age (<1%), and BMI (<1%). Compressed breast thickness had the greatest effect on average glandular dose. Breast density has a minor impact, while BMI and age have minimal impact on dose.