6th International Workshop on Breast Densitometry and Breast ...

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6 th <strong>International</strong> <strong>Workshop</strong> on Breast Densitometry
and Breast Cancer Risk Assessment
DUAL X-RAY ABSORPTIOMETRY AN ALTERNATIVE METHOD TO MEASURE
VOLUMETRIC BREAST DENSITY
Pereira A 1 , Shepherd J 2 , Garmendia ML 1 , Galleguillos B 1 , Ralph Highnam 3, Uauy R 1 , Corvalán C 1 .
1 Institute of Nutrition and Food Technology, University of Chile; 2 Department of Radiology and
Biomedical Imaging, University of California at San Francisco; 3 Mātakina Technology Limited,
Wellington, New Zealand
Background: Mammographic breast density (BD) is a strong risk factor for breast cancer; however its
use in adolescent populations is limited due to radiation exposure. Recently, applications to measure BD
have been developed for Dual X-Ray Absorptiometry (DXA) systems as a low-dose alternative method. A
previous validation study carried out in ~100 adult women showed a high correlation (r=0.70) between
volumetric breast density (%FGV) measured by DXA and area based mammographic BD. Since 2010, we
have followed the mothers of 550 girls participating in the Growth and Obesity Chilean Cohort Study to
assess nutritional determinants of increased BD. In these women, both mammograms and DXA scans of
the breasts were obtained. Our aims were i) to determine the precision of %FGV measured by DXA, and
ii) to assess the equivalency of %FGV, absolute fibroglandular volume (AFGV), and breast volume (BV)
measures made using DXA and mammograms.
Methods: In this cross-sectional study, 126 premenopausal women received both screening digital
mammograms (Hologic Selenia, Bedford, MA, USA) and breast DXA scans (GE iDXA, GE healthcare,
Madison, WI). Mammographic “raw” images were used to measure volumetric BD using a fullyautomated
commercial method (Volpara®, Matakina Technology, Wellington, New Zealand). For the
DXA scans, a left-right-left breast scanning protocol was used. The DXA analysis software was
developed by University of California at San Francisco. The end result was measures of %FGV, AFGV,
and BV by both mammography (Mx) and DXA. In addition, all women underwent anthropometric
measures (body mass index (BMI)=weight(kg)/height(mt) 2 ) and answered a sociodemographic
questionnaire. We estimated intraclass correlation coefficient (ICC) and the coefficient of variation
(precision) of DXA after repositioning, considering obesity (BMI>30), age (over 36 years) and BV (less
than 654 cm 3 ). Using linear regression models we estimated the correlation coefficient and R 2 between
volumetric BD measured with DXA (left image) and with Mx (MLO left image).
Results: The mean age was 37.1 years (sd=6.5) and 31.6% were obese. Mean time between
mammographic and DXA measurements was 9 months (sd=5.6). The ICCs for %FGV, AFGV and BV
after reposition the left breast were over 0.9 and the precision for %FGV, 3.7%; however the latter
declined to 5% in obese women and women with breast volumes less than 654 cm 3 . Mean values for
DXA and Mx are shown in Table 1. The correlation coefficients for %FGV, AFGV and BV between DXA
and Mx were all over 0.8 and the R 2 were 0.6, 0.7 and 0.8, respectively. The R 2 of %FGV increased to 0.8
if the time between both exams was less than six months.
ABSTRACTS
Discussion: DXA is a precise method to measure volumetric BD and it correlates better to volumetric
mammography measurements compared to area based models. These results suggest that DXA is a
reliable method to measure volumetric BD that can be used to continuously monitor BD in adult women
in follow-up studies
Table 1: Mean and standard deviation(sd) of breast composition using DXA and Mx
Breast Composition Data DXA (mean(sd)) Mx (mean(sd))
%FGV(%) 30.9(10.5) 10.2(5.2)
AFGV(cm 3 ) 214.4(98.8) 67.6(34.7)
BV(cm 3 ) 732.8(315.8 767.9(415.6)
Funding sources: Fondecyt 3130532 and 11100238, WCRF 2010/245 , Ellison Medical Foundation Grant to Ana Pereira
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