WOMEN with persistently dense or increasingly dense breasts face a higher risk of developing breast cancer compared to those with fatty breast tissue. Recent research aimed to identify groups of women with similar patterns of breast density changes over time and to assess how these trajectories influence breast cancer risk. Breast density, a known risk factor for breast cancer, changes over time and is influenced by factors such as age and hormonal status. Understanding these patterns could help refine breast cancer risk stratification and improve personalised screening strategies.
A retrospective cohort study was conducted using data from the Korean National Health Insurance Service. A total of 1,747,507 women aged 40 years or older who underwent four biennial mammographic screenings between 2009 and 2016 were included. Breast density was classified using the BI-RADS system. Group-based trajectory modelling identified five distinct breast density patterns. Breast cancer development was tracked until 31 December 2021, and Cox proportional hazard models were used to analyse the relationship between breast density trajectories and cancer risk
The five groups revealed diverse trajectories. Group 1 consisted of women with persistently fatty breast tissue, while group 2 had initially fatty tissue but increased density over time. Groups 3-5 included women with denser breast tissue, showing slight declines in density. Compared to group 1, women in group 2 had a 1.60-fold increased risk of breast cancer (95% CI: 1.49–1.72). Women in groups 3-5 faced even higher risks, with adjusted hazard ratios of 1.86 (95% CI: 1.74–1.98), 2.49 (95% CI: 2.33–2.65), and 3.07 (95% CI: 2.87–3.28), respectively. These findings held true across different age groups and regardless of changes in menopausal status or body mass index.
This study underscores the importance of considering breast density changes over time in breast cancer risk models. Persistently dense or increasingly dense breasts were strongly linked to higher cancer risks, emphasising the need for clinicians to incorporate these trajectories into screening and prevention strategies. Future research should focus on integrating longitudinal breast density data into personalised risk models to enhance early detection efforts.
Abigail Craig, EMJ
Reference
Park B et al. Trajectories of breast density change over time and subsequent breast cancer risk: longitudinal study. BMJ. 2024;387:e079575.
