Summary: The risk of getting breast cancer risk for those who have used hormone replacement therapy (HRT) varies by several factors.
Background: Studies have associated HRT with an increase in breast cancer risk. However, differential risks by body mass index (BMI) and breast density have been reported. In addition, studies on the effect of HRT use on breast cancer risk among black women have been inconsistent.
Current Study: Researchers from the University of Chicago (USA) analyzed 1,642,824 screening mammograms, including 9,300 breast cancer cases. All women were postmenopausal, and were part of the Breast Cancer Surveillance Consortium (a US screening mammogram registry). Data on HRT use were analyzed by race/ethnicity, age, BMI, and breast density.
Results: A greater than 20% increase in risk of breast cancer was associated with HRT among white and Hispanic women, but not black women. HRT was more strongly associated with with breast cancer risk in women with low or normal Body Mass Index, but not among those with a high BMI. In addition, women with denser breasts had an increased chance of getting breast cancer among those ho took HRT.
HRT was not linked with breast cancer for women with a high BMI and low breast density, but was associated with risk among those with low or normal BMI and high breast density.
My take: This study is the largest to date to investigate the association between HRT and breast cancer by covariables such as race/ethnicity, BMI, and breast density, Still a caveat is in order: The results were based on data for which we have no details regarding HRT type and duration of use.
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Reference: Journal of the National Cancer Institute, 03 September 2013