Comparison of breast density measured by dual energy X-ray absorptiometry with mammographic density among adult women in Hawaii

Background: While use of mammography is limited, due to concerns related to radiation exposure, dual energy X-ray absorptiometry (DXA), commonly available in medical care settings, is characterized by low radiation exposure. Methods: In the current paper, we compared breast density measured by DXA with mammographic density in 101 adult women who had a screening mammogram during the last 2 years. DXA scans of both breasts were taken using a clinical DXA system calibrated to measure breast density. The total projected breast area was manually delineated on each image and percent fibroglandular volume density (%FGV), absolute fibroglandular volume, total breast area and volume were computed. After digitizing mammographic films, total breast area, dense area, and percent density (PD) were estimated using computer-assisted mammographic density assessment. Results: Both DXA and mammographic measures showed high correlations between left and right breasts ranging from 0.85 to 0.98 (p < 0.0001). Mean %FGV was 38.8 ± 14.3%, and mean percent density was 31.9 ± 18.2% for craniocaudal views and 28.3 ± 16.2% for mediolateral views. The correlation between the two measures was 0.76 for both views (p < 0.0001). Associations with common risk factors showed similar patterns for DXA and mammographic densities; in particular, the inverse associations with BMI and age at menarche were evident for both methods. Multilinear regression with stepwise selection indicated an explained variance of 0.56 for %FGV alone and of 0.58 for %FGV plus number of children. Conclusion: Despite some differences in methodology, the current comparison suggests that DXA may provide a low-radiation option in evaluating breast density.