The distribution and determinants of mammographic density measures in Western Australian aboriginal women

Kirsty Mclean,Andrew Redfern,Jennifer Stone,Elizabeth Wylie,Helen Lund,Sandra Thompson,Leanne Pilkington,Ellie Darcey,Gemma Cadby,Christobel Saunders

doi:10.1186/s13058-019-1113-4

Abstract

BackgroundMammographic density (MD) is an established risk factor for breast cancer. There are significant ethnic differences in MD measures which are consistent with those for corresponding breast cancer risk. This is the first study investigating the distribution and determinants of MD measures within Aboriginal women of Western Australia (WA).MethodsEpidemiological data and mammographic images were obtained from 628 Aboriginal women and 624 age-, year of screen-, and screening location-matched non-Aboriginal women randomly selected from the BreastScreen Western Australia database. Women were cancer free at the time of their mammogram between 1989 and 2014. MD was measured using the Cumulus software. Kolmogorov-Smirnov tests were used to compare distributions of absolute dense area (DA), precent dense area (PDA), non-dense area (NDA) and total breast area between Aboriginal and non-Aboriginal women. General linear regression was used to estimate the determinants of MD, adjusting for age, NDA, hormone therapy use, family history, measures of socio-economic status and remoteness of residence for Aboriginal and non-Aboriginal women separately.ResultsAboriginal women were found to have lower DA and PDA and higher NDA than non-Aboriginal women. Age (p < 0.001) was negatively associated and several socio-economic indices (p < 0.001) were positively associated with DA and PDA in Aboriginal and non-Aboriginal women. Remoteness of residence was associated with both mammographic measures but for non-Aboriginal women only.ConclusionsAboriginal women have, on average, less MD than non-Aboriginal women but the factors associated with MD are similar for both sample populations. Since reduced MD is associated with improved sensitivity of mammography, this study suggests that mammographic screening is a particularly good test for Australian Indigenous women, a population that suffers from high breast cancer mortality.

Highlights

Mammographic density (MD) is the white radiographic appearance of epithelial and stromal tissue on a mammogram
Several studies have shown that MD measures are lower in South Asians, Japanese, Afro-Caribbean, African Americans, Asian Americans, and higher in Native Hawaiians and New Zealand Maori women compared to European women, consistent with breast cancer incidence rates [9,10,11,12,13]
Analysis of covariance adjusted for age and non-dense area (NDA) showed that mean dense area (DA) and precent dense area (PDA) were significantly lower in Aboriginal women compared to non-Aboriginal women

Summary

Introduction

Mammographic density (MD) is the white radiographic appearance of epithelial and stromal tissue on a mammogram. Genetic factors are thought to be a major determinant of MD [4, 5] but it appears that genetic factors primarily determine early life MD and environmental factors regulate later changes [6] This has important clinical implications for early identification of those at increased risk of breast cancer and/or at increased risk of a cancer going undetected, since MD is modifiable and reducing MD reduces breast cancer risk [7, 8]. There are significant ethnic differences in MD measures which are consistent with those for corresponding breast cancer risk This is the first study investigating the distribution and determinants of MD measures within Aboriginal women of Western Australia (WA)

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Conclusion