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Predictors of breast density change after hormone therapy cessation: results from a randomized trial
Sarah J Lowry1, Erin J Aiello Bowles, Melissa L Anderson
1Group Health Cooperative, Group Health Research Institute, Seattle, WA 98101, USA. lowry.s@ghc.org
Background:
Postmenopausal hormone therapy cessation is associated with a decrease in mammographic density (MD), but it is unknown whether this effect is modified by woman-level characteristics. We investigated whether we could identify characteristics of women who were most likely to experience a decrease in MD due to hormone therapy cessation.
Methods:
Postmenopausal hormone therapy users with a prior screening mammogram (n = 1,168) were randomized to continue hormone therapy or to suspend hormone therapy for 1 month or 2 months before their next screening mammogram. We estimated relative risks (RR) and attributable risks with 95% CIs of a ≥7.5% decrease in percentage MD (%MD) versus no change associated with hormone therapy cessation, stratified by age, body mass index (BMI), parity, and other factors.
Results:
Hormone therapy cessation increased a woman's likelihood of experiencing a ≥7.5% decrease in %MD by 30% (95% CI = 1.03-1.7), but we found little evidence of effect modification by age, race, BMI, change in BMI, baseline %MD, parity, family history of breast cancer, hormone therapy type, or duration of hormone therapy use.
Conclusions:
Woman-level factors do not appear to explain why some women experience a decrease in %MD following hormone therapy cessation and others do not.
Impact:
We were unable to identify subgroups of women who are more likely to experience a decrease in MD due to hormone therapy cessation; other factors, such as genetic factors, may be important determinants of hormone therapy-related changes in MD.
