Volumetric and area-based breast density measurement in the predicting risk of cancer at screening (PROCAS) study

Mammographic density, defined as the proportion of the breast area in a mammogram that contains fibroglandular tissue, is associated with risk of breast cancer. However, measures of mammographic density are subject to variation in the underlying imaging process and in the assessments of observers. Automatic volumetric measures of breast density remove much of this variability, but their association with risk is less well established. We present density measurements produced using area-based visual analogue scales (VAS) and by volumetric assessment software (QuantraTM, Hologic Inc.) in the PROCAS study. The distributions of VAS scores (n = 22 327) and volumetric quantities (n = 11 653) are given, as are their relationships for subjects with results by both (n = 11 096), but these are not directly comparable as one is area-based and the other volumetric. Inter-observer variability in visual area-based estimation is examined by a scatter plot matrix