Personalized mammography screening has emerged as the way of the future for improving breast cancer screening effectiveness. In order for individualized screening to be applicable in a clinical setting, one must first improve methods of evaluating individual risk by validating risk factors. Breast density, a measure of the dense tissue in the breast, has the potential to be used as a strong predictor for breast cancer risk. Strong evidence relating breast density and cancer risk has been established for 2-dimensional methods of estimating breast density, even with the subjective nature of that process. Considering that the breast is a 3-dimensional structure, efforts were made to develop methods to assess volumetric breast density (VBD). With the implementation of digital mammography in B.C., the quantitative analysis of mammograms to estimate VBD is now available. However, validation data to support the direct correlation of VBD to breast cancer risk for an ethnically diverse population like British Columbia is not available. 

This study aims to validate three-dimensional measures of breast density as a risk factor for breast cancer. Furthermore, the study will examine if and how VBD is associated with tumour characteristics, breast cancer subtypes and survival outcomes following treatment to better understand the biological mechanisms through which breast density influences breast tumour prognosis and to potentially provide a biomarker for risk of breast cancer recurrence. Screening mammograms and risk assessment questionnaires will be collected from 190,000 women in B.C. over two years. Women who are asymptomatic and aged 40 and older will be eligible to participate in the study and will be invited at their routine bilateral, two-view, screening mammogram.

Screening mammograms and questionnaires will be collected from twenty-two digital screening sites. Women in the study will be followed-up for 10 years. The breast cancer outcomes for the study participants will be extracted from the Screening Mammography Program of British Columbia (SMPBC) database. VBD measurements will be determined for all mammograms collected using Quantra and Volpara. The study will then establish the relative breast cancer risk attributable to mammographic density. The study will then examine whether there is a relationship between breast density and tumour characteristics, breast cancer subtypes and survival outcomes following treatment using data from the BC Cancer Registry. How well volumetric breast density represents the risk of developing breast cancer and predicts response to therapy and breast cancer recurrence, are critical pieces of information needed for a screening program to develop an effective personalized strategy to detect and treat breast cancer.

This study proposes to establish the direct link between VBD and breast cancer risk for women in British Columbia. Once substantiated, VBD, together with other risk factor information, will be necessary for the screening mammography program to develop effective personalized breast screening strategies such as ultrasound screening for women with dense breasts. Therefore the results of this study may have the potential to change the paradigm of early breast cancer detection from a uniform-screening method toward an individualized, risk/benefit based personal approach.