ASPO Abstracts
Air pollution and terminal duct lobular involution of the normal breast
Category: Molecular Epidemiology & Environment
Conference Year: 2020
Abstract Body:
Purpose: Air pollution has been associated with a higher risk of breast cancer. We examined whether air pollution
was associated with involution of terminal duct lobular units (TDLUs), the histologic site where most breast
cancers arise and an intermediate marker of breast cancer risk.
Methods: Pathologist enumerated TDLUs (i.e., TDLU count, a metric inversely associated with involution), were
assessed in H&E (Hematoxylin and Eosin)-stained breast tissue sections from 1,908 United States-residing
women ages 18-75 who donated to the Susan G. Komen Tissue Bank (2009-2012). The 2009 annual PM2.5 total
mass (µg/m3) at each woman's residential address was estimated from the Environmental Protection Agency's
Downscaler Model that combines Community Multiscale Air Quality (CMAQ) System modeling data with air quality
monitoring data. We secondarily considered CMAQ-modeled components of PM2.5 and gaseous pollutants. We
used K-means clustering to identify groups of individuals with similar levels of PM2.5 components, selecting 3
groups via cluster stability analysis. Relative rates (RRs) and 95% confidence intervals (95% CIs) for the
association between air pollutants and TDLU counts were estimated from a zero-inflated negative binomial
regression model adjusted for confounders.
Results: PM2.5 total mass was associated with higher TDLU count among all women (interquartile range (IQR)
increase, RR=1.03; 95% CI: 1.00-1.06). The magnitude of the PM2.5-TDLU count association was stronger
among postmenopausal women (RR=1.10; 95% CI: 1.03-1.18). Using K-means, we identified 3 groups that
corresponded to clusters that varied geographically and roughly represented high, medium, and low levels of
PM2.5 components. Compared to the cluster with low levels, the clusters with both high (RR=1.25; 95% CI: 0.95-
1.63) and medium (RR=1.24; 95% CI: 0.95-1.62) levels were associated with higher TDLU counts; associations
were again stronger among postmenopausal women.
Conclusions: Higher PM2.5 was associated with reduced TDLU involution as measured by TDLU counts. Air
pollution may influence the histologic characteristics of normal tissue which could in turn affect breast cancer risk.
This may be particularly relevant for the breast tissue of postmenopausal women.
Keywords: air pollution, terminal duct lobular units, breast cancer