Despite the epidemiological identification of breast cancer risk factors, incidence of the most commonly diagnosed breast cancer subtype (i.e., estrogen receptor positive) is increasing in Ireland and internationally. Examining the influence of established breast cancer risk factors on breast tumour phenotypes and mortality outcomes at the population level will improve understanding of how these factors contribute to tumour aggressiveness and build evidence for strategies aimed at improving the identification of women at highest risk of breast cancer. MBD is the white breast tissue seen radiologically on a breast mammogram and one of the strongest risk factors for breast cancer. This proposal aims to enhance breast cancer prevention efforts in Ireland by refining methods for MBD assessment, assessing MBD as a tool for understanding breast cancer clinical phenotypes and examining associations of MBD and mortality. This study will address the methodological issue of MBD assessment and will be conducted with Co-Applicants from the International Consortium of Mammographic Density (ICMD) at the International Agency for Research on Cancer (Lyon, France), where novel automated MBD assessment methods will be investigated, and compared to previously determined semi-automated methods. Additionally, this study will assess MBD and its associations with breast cancer clinical characteristics for the first time in BreastCheck, the National Breast Screening Programme in Ireland. Further, associations between MBD and breast cancer outcomes will be examined in this population. Collectively these investigations will build upon existing knowledge and provide important insights into the influence of MBD on clinical outcomes internationally within ICMD and nationally within BreastCheck. With an increasing focus on precision prevention medicine and the development of personalised breast cancer screening programmes, there is an urgent need to leverage established aetiological knowledge to improve strategies for breast cancer prevention through collaborative, integrative population-based approaches. This study will be a step towards this goal.
