Breast density notification: evidence on whether benefit outweighs harm is required to inform future screening practice

Breast density is one of a number of independent risk factors for breast cancer. Having dense breasts (heterogeneously dense or extremely dense) is prevalent in 40%–50% of women in the breast screening population, making it one of the most common risk factors for breast cancer. Separate from this, having dense breasts also increases a woman’s risk of having a breast cancer missed on mammography, meaning that it increases the risk of having an interval cancer diagnosed before the next scheduled mammogram in screening participants. This is due to the lower sensitivity of mammography in women with dense breast tissue.

Over the past decade, breast density has been a major topic of international discussion among women, physicians and policy-makers as a way to manage the risk of breast cancer.5 In the USA, unprecedented legislation has been enacted in 38 states and the District of Columbia to notify women about their breast density. Following on from this, in early 2019, the US Congress passed national breast density legislation which proposes that the US Food and Drug Administration ensures that all mammography facilities include breast density information in reports sent to patients and their physicians. This legislation has been driven by complex social phenomena, largely stemming from industry interest, consumer advocacy groups demanding that women be informed and concerns about the burden of missed cancers.