Volumetric quantification of the effect of aging and hormone replacement therapy on breast composition from digital mammograms.

Objective: To assess the physiological changes in breast composition with aging using volumetric breast composition measurement from digital mammograms and to assess the effect of hormone replacement therapy (HRT).

Methods: A total of 764 consecutive mammograms of 208 non-HRT using women and 508 mammograms of 134 HRT-using women were analyzed using a volumetric breast composition assessment software (Quantra™, Hologic Inc.). Fibroglandular tissue volume (FTV), breast volume (BV), and percent density (PD) were measured. For statistical analysis, women were divided into a premenopausal (<46 years), a perimenopausal (46-55 years), and a postmenopausal (>55 years) age group. More detailed graphical analysis was performed using smaller age brackets. Women using HRT were compared to age-matched controls not using HRT.

Results: Women in the postmenopausal age group had a significantly lower FTV and PD and a significantly higher BV than women in the premenopausal age group (FTV: 77 vs. 120 cm(3), respectively; PD: 16% vs. 28%, respectively; BV 478 vs. 406 cm(3), respectively; p<0.01 for all). Median FTV was nearly stable in consecutive mammograms in the premenopausal and postmenopausal age groups, but declined at a rate of 3.9% per year in the perimenopausal period. Median PD was constant in the premenopausal and postmenopausal age groups and declined at a rate of 0.57% per year in the perimenopausal age group. BV continuously increased with age. Women using HRT throughout the study had a 5% higher PD than women not using HRT (22% vs. 17%, respectively; p<0.001).

Conclusions: Accurate knowledge of normal changes in breast composition are of particular interest nowadays due to the importance of breast density for breast cancer risk evaluation. FTV and PD change significantly during the perimenopausal period but remain relatively constant before and thereafter. Median total breast volume consistently increases with age and further contributes to changes in breast density. HRT use is associated with a significantly higher PD.