Abstract P5-08-20: Association between quantitative mammographic density and breast cancer subtypes among Chinese breast cancer patients

Abstract

Abstract High mammographic density (MD) is a strong risk factor for breast cancer; however, data on the association between MD and breast cancer subtypes has been inconsistent and most studies have been conducted using data from Western women. Studies have shown that Asian women, who in general have denser breasts compared with Western women, were more likely to develop luminal B and HER2-enriched tumors. We previously reported that higher MD, assessed using Breast Imaging Reporting and Data System (BI-RADS) categories, was associated with HER2-enriched tumors among Chinese breast cancer patients, which may at least partially explain the higher incidence of HER2-enriched tumors observed in Asian women. Since BI-RADS MD measurement is categorical and known to be subjective, in this study, we aimed to re-evaluate the MD-subtype association using an automated quantitative density metric. The analysis included 1,549 women with invasive breast cancer who were diagnosed and treated in a tertiary hospital in Beijing, China. Subtypes were defined as Luminal A (n=606): ER+ and PR+, HER2-, and low Ki-67 (<30% positive staining)/grade (grades 1 or 2); luminal B/HER2- (n=446): ER+ and/or PR+, HER2-, and high Ki-67 (≥30%)/grade (grade 3); luminal B/HER2+ (n=182): ER+ and/or PR+, HER2+ (regardless of Ki-67/grade); HER2-enriched (n=121): ER-, PR-, and HER2+; Triple-negative (TN, n=194): ER-, PR-, and HER2-. Quantitative measures of MD for the contralateral unaffected breast, including total breast volume, fibroglandular volume, and Volpara Density Grade (VDG, based on predetermined cut-points from volumetric percent density that shows moderate agreement with visual BI-RADS categories), were obtained using VolparaDensity software. Polychotomous logistic regression was used to assess the association between MD (per 1-unit standard deviation increase) and breast cancer subtypes with the adjustment of age, menopausal status, parity, and body mass index (BMI). Compared with luminal A cases, cases with luminal B/HER2- (Odds ratio [OR], 1.15; 95% confidence interval [CI], 1.01-1.32; p=0.04), luminal B/HER2+ (OR, 1.22; 95% CI, 1.02-1.44; p=0.03), and HER2-enriched (OR, 1.32; 95% CI, 1.08-1.60; p=0.01) tumors had significantly higher fibroglandular dense volume, and these associations were stronger in women with normal BMI. In contrast, cases with TN tumors had lower non-dense volume compared with luminal A cases (OR, 0.83; 95% CI, 0.69-1.00; p=0.05). Percent density did not vary significantly by subtypes. When comparing dense versus non-dense breasts using VDG, we found that dense breasts were significantly associated with HER2-enriched tumors (OR, 2.49; 95% CI, 1.40-4.42; p=0.002). Our data suggest that increasing dense volume was associated with luminal B and HER2-enriched subtypes among Chinese breast cancer cases. These results may provide insight into the distinct distribution of breast cancer subtypes in Asian populations. Citation Format: Xiaohong R Yang, Yuan Tian, Jennifer Guida, Hela Koka, Ariane Chan, Changyuan Guo, Erni Li, Eric Tang, Hyuna Sung, Ning Lu, Nan Hu, Gretchen Gierach, Jing Li. Association between quantitative mammographic density and breast cancer subtypes among Chinese breast cancer patients [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P5-08-20.