Abstract C18: The association between breast tissue optical content and percent density and dense area in pre- and postmenopausal women
Authors: Blackmore Kristina M. , Knight Julia A. , Walter Jane , Lilge Lothar 
Published: May 2019

Abstract
Optical spectroscopy (OS) is a method of evaluating breast tissue that involves no exposure to ionizing radiation and no discomfort, unlike mammography. Red and near-infrared light is shined through the breast and light scattering and absorption spectra provide information on the breast content of water, lipid, and hemoglobins (oxy and deoxy). Previously, we demonstrated that OS scores derived from Principal Component Analysis of spectra were associated with quantitative mammographic features of the breast (percent density, dense area). Here, we examine the relationship between optically derived breast concentrations of water (%), lipid (%), total hemoglobin (μM), tissue oxygen saturation (%), and scattering parameters (amplitude, power) and percent density and dense area in these pre (n = 95) and post-menopausal (n = 107) women.
Participants were recruited from the Breast Imaging Centre at Mount Sinai Hospital in Toronto. Information concerning their age, menopausal status, height and weight were collected using a self-administered questionnaire. For each woman, OS measurements were done in four standardized positions (center, medial, distal, lateral) on each breast, providing optical interrogation of different anatomical regions. A spectrally constrained global fitting procedure using a model of diffuse light transport was used to estimate tissue composition (hemoglobins, lipids, water) and scattering parameters (amplitude, power) at each measured position on both breasts. These results were then averaged over each position over both breasts. Percent mammographic density (PD) and dense area (DA) were estimated from digitized film mammograms using Cumulus. For each woman, PD and DA were averaged over both breasts and square root transformed. The association between OS breast tissue content at the distal position and quantitative mammographic features was analyzed using linear regression analysis stratified by menopausal status and adjusted for body mass index (PD only).
Among pre-menopausal women, lipid content was significantly inversely associated with both PD (β = -0.050, p = 0.0002) and DA (β = -0.046, p = 0.019), while water content was significantly positively associated with PD only (β = 0.057, p = 0.008). Tissue oxygen saturation was marginally inversely associated with PD (β = -0.033, p = 0.057) and strongly inversely associated with DA (β = -0.098, p = 0.002). Among post-menopausal woman, both lipid and water content were significantly and strongly associated with PD (lipid: β = -0.084, p &lt; 0.0001; water: β = 0.135, p &lt; 0.0001) and DA (lipid: β = -0.096, p &lt; 0.0001; water: β = 0.113, p = 0.001).
The association between breast tissue content (hemoglobin, lipid, water) derived from OS and PD and DA in pre- and post-menopausal women is consistent with a higher amount of proliferating tissue in younger women (lower tissue oxygen saturation in more dense breasts). Greater lipid associated content was observed in lower density breast tissue while higher water content characterized higher density breast tissue. PD, and to a lesser extent DA, are recognized risk factors for breast cancer. OS may be useful for assessing physiologic tissue differences related to breast cancer risk and/or measuring differences from cumulative exposure to factors known to modulate risk, particularly in younger woman where mammography is not an option.
Citation Format: Kristina M. Blackmore, Julia A. Knight, Jane Walter, Lothar Lilge. The association between breast tissue optical content and percent density and dense area in pre- and postmenopausal women. [abstract]. In: Proceedings of the Twelfth Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2013 Oct 27-30; National Harbor, MD. Philadelphia (PA): AACR; Can Prev Res 2013;6(11 Suppl): Abstract nr C18.