Background: Higher mammographic breast density is a strong risk factor for breast cancer. Early-life factors may influence breast development and subsequent breast density in adulthood. Although childhood adiposity is inversely associated with breast cancer risk, the association of childhood adiposity with mammographic breast density in premenopausal women has not been adequately studied. This knowledge could provide insight into pathways linking mammographic density and breast cancer risk. We investigated the associations between adiposity at age 10 and mammographic density.

Methods: We collected data from 370 premenopausal women during their routine screening mammograms at Washington University in St. Louis, MO from December 2015 to October 2016. Body size at age 10 was self-reported using the Stunkard 9-figure Somatotype pictogram. For these analyses, the Stunkard pictogram was collapsed into 4 groups: (i) body size 1 or 2, (ii) body size 3 or 4, (iii) body size 5, (iv) body size 6 or higher. Body mass index (BMI) at age 10 was imputed using BMI and Stunkard data from the Growing Up Today Study. Trained personnel collected womens' height and weight, which were used to calculate current BMI. We used the Volpara software to evaluate the following volumetric mammographic density measures: volumetric percent density (VPD), dense volume (DV) and non-dense volume (NDV). Age-adjusted Pearson correlations and multivariable linear regression models (adjusted for age, age at each given birth, family history, race, education, oral contraceptive use, and breast feeding history) were used to evaluate the associations between adiposity at age 10 and volumetric mammographic density measures.

Results: The mean age at the time of screening mammogram was 47.1 years. The majority of the women (43.8%) reported having body size 1 or 2, followed by body size 3 or 4 (34.9%), body size 5 (13.8%) and body size 6 (7.6%) at age 10. We observed a negative correlation between BMI at age 10 (r= -0.28, p-value<0.001) and VPD, and a positive correlation between BMI at age 10 (r= 0.27, p-value<0.001) and NDV. In multivariable regression models, adiposity at age 10 was significantly inversely associated with VPD, and positively associated with NDV. A 1kg/m2 increase in BMI at age 10 was associated with a 6.3% decrease in VPD (p-value <0.001), and a 6.7% increase in NDV (p-value <0.001). Compared to women whose body sizes were 1 and 2 at age 10, women with body size 3 or 4 had a 17.6% decrease in VPD, and a 28.5% increase in NDV; women with body size 5 had a 32.3% decrease in VPD, and a 58.1% increase in NDV, and women with body sizes ≥6 had a 46.6% decrease in VPD, and a 75.1% increase in NDV (all p-values <0.05). The associations of body size at age 10 and VPD were attenuated, but still statistically significant when we adjusted for current BMI. No statistically significant associations were found between adiposity at age 10 and DV.

Conclusions: Our findings of an inverse association between adiposity at age 10 and percent density suggest that adiposity at age 10 could impact breast cancer development via its effect on mammographic density. Mechanistic studies to understand how childhood adiposity reduces mammographic density and breast cancer development in premenopausal women are needed.

Citation Format: Alimujiang A, Imm KR, Appleton CM, Colditz GA, Berkey CS, Toriola AT. Adiposity at age 10 and mammographic density among premenopausal women [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P4-01-01.