RACIAL DIFFERENCES IN MAMMOGRAPHIC DENSITY IN BRAZIL: IMPLICATIONS FOR MAMMOGRAPHIC SCREEN

Background: Mammographic density (MD) is a stronger biomarker of susceptibility to breast cancer and a major determinant of the sensitivity of mammographic screening. This study examined for the first time racial differences in MD in Brazil. Methods: 555 women (215 from the Longitudinal Study of Adult Health - ELSA-Brasil and 340 users of SUS) in Bahia were enrolled into the study. Participants completed an interview, had their heights and weights measured, and underwent a 2-view digital mammography of each breast. MD was measured on the left MLO image using the semi-automated Cumulus software, and expressed as the percentage (PMD) of the breast area occupied by fibroglandular tissue. Linear regression models were fitted to assess ethnicity–PMD associations adjusting for age, body mass index and reading batch and further for socio-economic and reproductive variables. Results: The study population comprised 95 White (W), 270 Brown-mixed (Bm) and 169 Black (B) women, with a mean age of 58 (SD=5.4) years. 63% W, 69% Bm and 49% B women had low educational level; 24% W, 47% Bm and 31% B women had ≥4 children. Adjusted analysis showed that relative to W women, PMD was 23% (1.23; 95% CI 1.04-1.45) higher in Bm and 4% (1.04; 0.89-1.21) higher in B; however, further adjustment for socio-economic and reproductive variables attenuated the racial differences (16% (1.16; 0.96-1.40) and 9% (1.09; 0.92-1.29) for Bm and B, respectively. Conclusions: The racial differences in PMD were mainly accounted by ethnic differences in socio-economic and reproductive-related factors.