Abstract P3-01-26: Mammographic density in relation to breast cancer risk factors among Chinese women

Abstract Higher mammographic density (MD) is a known risk factor for breast cancer (BC), however, studies examining determinants of density in Chinese populations are limited. Asian women tend to have higher MD compared to European women, and yet they have a lower overall BC incidence rate. The goal of this study was to investigate the influence of established BC risk factors on quantitatively measured MD among Chinese women. The study population included 7,351 Chinese women, who had mammograms at the National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China, between 2016 and 2017 for different indications, including but not limited to screening exam, breast pain, and suspected breast tumors. Only subjects with BI-RADS (Breast Imaging-Reporting and Data System) diagnostic classification of 1 (negative, n= 2,293), 2 (benign, n= 3,519), and 3 (probably benign, n= 1,539) were included in this analysis. VolparaDensity software was used to obtain quantitative MD measures including absolute dense breast volume and percent breast density. We conducted multivariable linear regression modeling on each density measurement to test for its associations with well-established breast cancer risk factors. The mean age of this study population was 50.1 years old (range= (25, 82)), the average body mass index (BMI) was 24.0 kg/m2 (range= (14.2, 48.9)), and about 46% of women were postmenopausal. The mean absolute dense and percent dense volumes were 58.4 (SD= 32.1) and 14.8 (SD= 7.1, equivalent to Volpara Density Grade= 3), respectively. Associations between quantitative MD measures and BC risk factors did not vary significantly across the three BI-RADS diagnostic classes and we therefore combined these patients in subsequent analyses. Most risk factors we examined showed similar associations with dense volume and percent density. For example, both dense volume and percent density were inversely associated with age, parity, longer duration (> 1 year) of breastfeeding, and postmenopausal status, while they were positively associated with age at menopause. In contrast, the associations with age at menarche and BMI showed opposite directions for dense volume and percent density. While increasing BMI was positively associated with dense volume, it was inversely associated with percent density. Age at menarche, however, was inversely correlated with dense volume, but positively associated with percent density. When stratifying by menopausal status, the associations for age, BMI, and parity were similar among pre- and post-menopausal women, while the associations for age at first birth and breastfeeding were stronger among postmenopausal women. In general, observed breast cancer risk factor associations with quantitative breast density metrics in this Chinese population are similar to those previously reported in Western women. We did not observe striking differences in associations of breast density with reproductive factors and BMI among Asian women in this large analysis based on quantitative density measurements. Other risk factors such as genetic susceptibility loci associated with MD should be examined in large Asian studies to further our understanding on how MD influences breast cancer risk in Asian populations. Citation Format: Hela Koka, Yuan Tian, Deng Lu, Kai Yu, Er-Ni Li, Changyuan Guo, Bin Zhu, Jennifer L Guida, Ariane Chan, Nan Hu, Ning Lu, Gretchen Gierach, Jing Li, Xiaohong R Yang. Mammographic density in relation to breast cancer risk factors among Chinese women [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-01-26.