Australian Women's Intentions and Psychological Outcomes Related to Breast Density Notification and Information: A Randomized Clinical Trial.

Importance: Whether the benefits of notifying women about breast density outweigh the potential harms to inform current and future mammogram screening practice remains unknown.

Objective: To assess the effect of mammographic breast density notification and information provision on women's intention to seek supplemental screening and psychological outcomes.

Design, Setting, And Participants: A 3-arm online randomized clinical trial was conducted from August 10 to 31, 2021. Data analysis was conducted from September 1 to October 20, 2021. Participants included Australian residents identifying as female, aged between 40 and 74 years, with no history of breast cancer who were residing in jurisdictions without existing breast density notification with screening mammograms.

Interventions: Women were randomized to receive 1 of the following hypothetical breast screening test result letters: screening mammogram result letter without breast density messaging (control), screening mammogram result letter with breast density messaging and an existing density information letter taken from a screening service in Australia (intervention 1), and screening mammogram result letter with breast density messaging and a health literacy-sensitive version of the letter adapted for people with lower health literacy (intervention 2).

Main Outcomes And Measures: Primary outcomes were intention to seek supplemental screening; feeling anxious (uneasy, worried, or nervous), informed, or confused; and having breast cancer worry.

Results: A total of 1420 Australian women were randomized and included in the final analysis. The largest group consisted of 603 women aged 60 to 74 years (42.5%). Compared with the control cohort (n = 480), women who received density notification via intervention 1 (n = 470) and intervention 2 (n = 470) reported a significantly higher intention to seek supplemental screening (0.8% vs 15.6% and 14.2%; P < .001) and feeling anxious (14.2% vs 49.4% and 48.5%; P < .001), confusion (7.8% vs 24.0% and 23.6%; P < .001), and worry about breast cancer (quite/very worried: 6.9% vs 17.2% and 15.5%; P < .001). There were no statistically significant differences in these outcomes between the 2 intervention groups.

Conclusions And Relevance: In this randomized clinical trial, breast density notification and information integrated with screening mammogram results increased women's intention to seek supplemental screening and made women feel anxious, confused, or worried about breast cancer. These findings have relevance and implications for mammogram screening services and policy makers considering whether and, if so, how best to implement widespread notification of breast density as part of mammography screening.

Trial Registration: ACTRN12621000253808.