Using an automated measure of breast density to explore the association between ethnicity and mammographic density in Australian women.

Introduction: The aim of this study was to investigate mammographic density in a sample of Victorian women and explore a possible association between mammographic density and ethnicity.

Methods: Categories of mammographic density, using Volpara Density Grade, were reported using two editions of Volpara automated software in a data set of women attending two Victorian sites for mammographic screening. The variables available for analysis were age, self-reported exposure to menopausal hormone therapy (MHT) and ethnicity based on country of birth.

Results: Data from 16,943 women were available for analysis. Using the VDG 4th edition, 40% of women were classified in the higher two categories (42% for the 5th edition) and 76.9% of women were in the same VDG category using both systems. In the sample, 87.7% of women were in the age range currently invited for screening in Victoria (50-74 years). Of the total group, 82.5% could be classified on the basis of country of birth. In multivariable logistic regression analyses examining factors associated with higher VDG, age (protective), use of MHT (risk factor) and being born in a country with predominantly Asian ancestry (risk factor) were all statistically significant at P < 0.001 for both editions irrespective of whether the reference category was the lowest two or three VDG categories.

Conclusions: Mammographic density as assessed by VDG was positively associated with ever exposure to MHT and inversely associated with age. Being born in a country with predominantly Asian ancestry was associated with higher VDG when controlled for age and MHT exposure.