Longitudinal changes of automated volumetric breast density with postmenopausal hormone therapy

To evaluate how volumetric percent density (VPD) changes longitudinally with postmenopausal hormone therapy (HT).

Medical records of 297 women who visited the outpatient clinic in a tertiary medical center between 2011 and 2019 were retrospectively reviewed. Study participants were postmenopausal hormone never-users (n = 103), estrogen therapy (ET) users (n = 95), and estrogen plus progestogen (EPT) users (n = 99). All hormone users were naïve to HT before the study. VPD was measured at least twice over 3 years, and was measured before and after HT in all hormone users. Longitudinal VPD changes were analyzed using a linear mixed effects model adjusted for age and body mass index (BMI) at index mammography.

The mean age (standard deviation) of study participants at index mammography was 53.0 years (3.3 years). Baseline characteristics, including baseline VPD, were similar across the three groups. After adjustment for age and BMI, the predicted slopes of annual VPD change did not differ among never-users, ET users, and EPT users (-6.8 % (95 % CI -12.1 % to -1.6 %), 0.2 % (95 % CI -4.4 % to 4.8 %), and 0.4 % (95 % CI -5.1 % to 4.3 %), respectively (P = 0.21)). Furthermore, subgroup analyses stratified by estrogen formulation did not demonstrate any difference in the slopes of annual VPD change among never-users, conjugated equine estrogen users, estradiol valerate users, and EPT users (-7.0 %, -1.2 %, 4.9 %, and -0.5 %, respectively; P = 0.27).

The predicted annual VPD change did not differ by HT during 3 years of follow-up. Neither ET nor EPT increased VPD.