Mammographic density in relation to breast cancer risk factors among Chinese women.

Background Increased mammographic density (MD) is a known breast cancer (BC) risk factor, but its influencing factors are unclear in Asian populations. This study examined the links between known BC risk factors and quantitatively measured MD in 7,351 Chinese women with non-malignant mammographic findings. Methods VolparaDensity software quantified volumetric MD measures: total breast (TBV), absolute dense (ADV), percent dense (PDV= ADV/TBV), and non-dense volumes (NDV= TBV-ADV). Multivariable linear regression models assessed associations between these MD metrics and BC risk factors. Results The mean age of the population was 50.1 (SD=8.3) years. The mean ADV, NDV, and PDV were 58.4 (SD=32.1), 382.8 (SD=202.0) cm³ and 14.8 (SD=7.1) %, respectively. PDV was inversely associated with age, weight, body mass index (BMI), parity, breastfeeding duration, and postmenopausal status, but positively linked to height and age at menopause. NDV showed opposite associations. ADV had similar associations to PDV, except for height, weight, and BMI, which differed for women with the lowest NDV. PDV associations with age at menarche, age at first birth, and breastfeeding duration varied by BMI and menopausal status. Conclusions MD may influence the relationship between reproductive factors and BC risk, depending on MD measure, menopausal status, and BMI. Impact This study examines how quantitative MD measures relate to known BC risk factors in an East Asian population, factoring in menopausal status and BMI. The results underscore the complex role of MD and confounding factors in BC risk, highlighting the need for tailored insights for future research and screening.