Endocrine Abstracts

Introduction: Women with a high breast density have an increased risk of breast cancer, which prevalence increases after menopause in obese subjects. Breast density can be calculated on mammograms as the proportion of dense tissue (percent mammographic density-PMD). Several factors may influence the PMD, including age, menopausal status, body mass index (BMI), and bone mineral density (BMD) taken as an index of overall estrogen exposure. However, conflicting data have been reported, possibly due to the heterogeneity of large populations. We aimed to determine which factors influence PMD in a series of postmenopausal women at a single center, excluding those with early menopause (<40 yrs).

Methods: A hundred of post-menopausal women (median age 61 yrs-old, range 50-83) was studied in the last year. The median age at menopause was 50 yrs (42–57), median BMI was 27.5 kg/m² (17.58–41.62) and 36 patients (36%) were obese (BMI>30 kg/m²). PMD was calculated on bi-dimensional mammographic projections of the left breast. Lumbar, total and neck femoral BMD (g/cm²) was evaluated by MOC-DEXA (Lunar, GE). Non-parametric statistical analysis (Spearman correlations, Wilcoxon-test) was performed (JMP 11.0, SAS, USA).

Results: A significant negative correlation was found between BMI and PMD (P=0.0026; ρ=−0.298), but PMD was not significantly influenced by age, age at menopause, duration of menopause or BMD on the whole series. In contrast, a significant positive correlation was found between BMI and BMD (P<0.0001 and ρ> 0.40 at all bone districts). PMD tended to be lower in obese women (P=0.068 vs non-obese) but the degree of obesity (BMI) did not appear to significantly influence PMD or BMD in this group. In contrast, the differential impact of BMI on PMD (P=0.0026, ρ=−0.370) and BMD at any bone district was confirmed in non-obese women, in particular at the total femoral site (P<0.0001, ρ=0.483). In addition, the non-obese group was characterized by a significant negative correlation between PMD, patient’s age (P=0.0086, ρ=−0.326) and menopause duration (P=0.002, ρ=−0.319).

Conclusion: BMI has a differential impact on PMD and BMD after menopause, probably accounting for some conflicting data in the literature. Increased estrogen exposure, increased breast adiposity and long-term persistence the fibro-glandular breast tissue may contribute to the increased risk of breast cancer after menopause in obese women, suggesting a complex interplay between endocrine and paracrine factors.