Breast Cancer Risk Differs by Race, BMI, Breast Density Among Hormone Replacement Therapy Users
In a study reported in the Journal of the National Cancer Institute, Ningqi Hou, PhD, of University of Chicago, and colleagues analyzed the potential contribution of patient characteristics to risk of breast cancer associated with hormone replacement therapy. The study found that risk of breast cancer in this setting varies according to race/ethnicity, body mass index (BMI), and breast density.
Study Details
The analysis included 1,642,824 screening mammograms with 9,300 breast cancer cases in postmenopausal women aged ≥ 45 years from the Breast Cancer Surveillance Consortium, a longitudinal registry of mammography screening in the United States. Among these women, 62.7% were non-Hispanic white, 4.8% non-Hispanic black, 3.2% Asian/Pacific Islander, 6.3% Hispanic, 1.2% other or mixed racial/ethnic background, and 21.9% unknown. Overall, 44.4% were hormone replacement therapy users, 41.6% nonusers, and 14.0% had unknown hormone replacement therapy status. Hormone replacement therapy users had a higher incidence of breast cancer compared with nonusers (5.78 vs 5.46 per 1,000).
Logistic regression was performed to estimate odds ratios for breast cancer associated with hormone replacement therapy use according to race/ethnicity, age, BMI, and breast density. Multiple imputation methods were used to accommodate missing data for hormone replacement therapy use and other covariables.
Factors Associated With Increased Risk
Hormone replacement therapy use was associated with > 20% increased risk in white (odds ratio [OR] = 1.21, 95% confidence interval [CI] = 1.14–1.28), Asian (OR = 1.58, 95% CI = 1.18–2.11), and Hispanic women (OR = 1.35, 95% CI = 1.09–1.67) but not in black women (OR = 0.91, 95% CI 0.72–1.14; P = .04 for interaction). Lower BMI (P = .01 for interaction) and denser breasts (P = .004 for interaction) were associated with increased risk for breast cancer among hormone replacement therapy users.
Since breast density was inversely correlated with BMI and both modified the association between hormone replacement therapy use and breast cancer risk, a multivariate analysis including effects of both factors was performed. This analysis showed that hormone replacement therapy use was associated with increased breast cancer risk in underweight or normal weight women (BMI = 10–24.99 kg/m2) with extremely dense breasts (OR = 1.49, 95% CI = 1.21–1.83), heterogeneously dense breasts (OR = 1.40, 95% CI = 1.25–1.57), or scattered fibroglandular densities (OR = 1.25, 95% CI = 1.09–1.43) and in overweight women (BMI = 25–29.99 kg/m2) with extremely dense breasts (OR = 1.29, 95% CI = 1.01–1.66) or heterogeneously dense breasts (OR = 1.21, 95% CI = 1.06–1.39). In overweight/obese women (BMI > 25 kg/m2) with less-dense breasts (scattered fibroglandular densities or almost entirely fat), no excess risk was associated with hormone replacement therapy use (adjusted ORs = 0.96–1.08).
The investigators concluded, “The impact of [hormone replacement therapy] use on breast cancer risk varies according to race/ethnicity, BMI, and breast density. This risk stratification could help in advising [hormone replacement therapy] use for the relief of menopausal symptoms.”
Dezheng Huo, MD, PhD, of University of Chicago, is the corresponding author for the Journal of the National Cancer Institute article.
The study was supported in part by the American Cancer Society.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
