Mammographic density and breast cancer risk in White and African American Women
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Mammographic density is a strong risk factor for breast cancer, but limited data are available in African American (AA) women. We examined the association between mammographic density and breast cancer risk in AA and white women. Cases (n = 491) and controls (n = 528) were from the Carolina Breast Cancer Study (CBCS) who also had mammograms recorded in the Carolina Mammography Registry (CMR). Mammographic density was reported to CMR using Breast Imaging Reporting and Data System (BI-RADS) categories. Increasing mammographic density was associated with increased breast cancer risk among all women. After adjusting for potential confounders, a monotonically increasing risk of breast cancer was observed between the highest versus the lowest BI-RADS density categories [OR = 2.45, (95 % confidence interval: 0.99, 6.09)]. The association was stronger in whites, with ~40 % higher risk among those with extremely dense breasts compared to those with scattered fibroglandular densities [1.39, (0.75, 2.55)]. In AA women, the same comparison suggested lower risk [0.75, (0.30, 1.91)]. Because age, obesity, and exogenous hormones have strong associations with breast cancer risk, mammographic density, and race in the CBCS, effect measure modification by these factors was considered. Consistent with previous literature, density-associated risk was greatest among those with BMI > 30 and current hormone users (P value = 0.02 and 0.01, respectively). In the CBCS, mammographic density is associated with increased breast cancer risk, with some suggestion of effect measure modification by race, although results were not statistically significant. However, exposures such as BMI and hormone therapy may be important modifiers of this association and merit further investigation.
KeywordsMammographic breast density Breast cancer Race African American Epidemiology
List of abbreviations
Breast Imaging Reporting and Data System
Body mass index
Carolina Breast Cancer Study
Carolina Mammography Registry
Likelihood ratio test
National Heart, Lung, and Blood Institute
The authors are grateful to Jessica Tse and Robert Christopher Allis for their assistance with data management and data analysis for this manuscript. This research was supported [in part] by the Intramural Research Program of the NIH and the National Cancer Institute. M.A.T was supported by the National Institutes for Environmental Health Sciences and National Cancer Institute Breast Cancer and the Environment Research Program 5U01ES019472-02 and NCI grant 5R01CA138255. R.C.M. and M.A.T are supported by a SPORE in Breast Cancer 5P50CA058233.
Conflict of interest
The authors declare that they have no conflict of interest.
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