Associations between mammographic density and tumor characteristics in Chinese women with breast cancer

PurposeMammographic density (MD) is a strong risk factor for breast cancer, yet its relationship with tumor characteristics is not well established, particularly in Asian populations.MethodsMD was assessed from a total of 2001 Chinese breast cancer patients using Breast Imaging Reporting and Data System (BI-RADS) categories. Molecular subtypes were defined using immunohistochemical status on ER, PR, HER2, and Ki-67, as well as tumor grade. Multinomial logistic regression was used to test associations between MD and molecular subtype (luminal A=reference) adjusting for age, body mass index (BMI), menopausal status, parity, and nodal status.ResultsThe mean age at diagnosis was 51.7years (SD=10.7) and the average BMI was 24.7kg/m(2) (SD=3.8). The distribution of BI-RADS categories was 7.4% A=almost entirely fat, 24.2% B=scattered fibroglandular dense, 49.4% C=heterogeneously dense, and 19.0% D=extremely dense. Compared to women with BI-RADS=A/B, women with BI-RADS=D were more likely to have HER2-enriched tumors (OR=1.81, 95% CI 1.08-3.06, p=0.03), regardless of menopausal status. The association was only observed in women with normal (<25kg/m(2)) BMI (OR=2.43, 95% CI 1.24-4.76, p<0.01), but not among overweight/obese women (OR: 0.98, 95% CI 0.38-2.52, p=0.96).ConclusionsAmong Chinese women with normal BMI, higher breast density was associated with HER2-enriched tumors. The results may partially explain the higher proportion of HER2+tumors previously reported in Asian women.