The impact of legislation mandating breast density notification - Review of the evidence.

Breast density (BD) is an independent risk factor for breast cancer and reduces the sensitivity of mammography. The enactment of BD legislation in a majority of states in the USA mandating notification of risks associated with BD directly to women undergoing mammography has catapulted interest in BD among women, physicians, and policymakers. We therefore report a descriptive review of the evidence on the impact of enactment of BD legislation. Based on 22 eligible studies, we identified four broad themes of research: studies of the impact on screening rates, most showing increased utilisation of supplemental screening; studies exploring the effect on women, radiologists, or primary physicians (reporting heterogeneous effects on knowledge, awareness, perceptions, attitudes and behaviour; and changes in practice); few studies assessing the population impact (effect on screening outcomes or breast cancer stage); and studies of costs highlighting the economic burden from supplemental screening. Given that many of the studies were retrospective single institution studies (comparing pre- and post-legislation) or small surveys with a paucity of population-level studies, we highlight areas meriting additional research. The information described in this review can inform research priorities where BD legislation has been introduced and can be used to guide world-wide policy or practice decisions where BD legislation may be under debate or contemplation.