The impact of hormone replacement therapy (HRT) use on breast cancer risk varies according to patient race/ethnicity, body mass index (BMI), and breast density, researchers have learned. Their findings indicate that black women, obese women, and women whose breasts are less dense (contain more fatty tissue than connective tissue) may be the HRT users who incur the least excess risk for breast cancer.     

Studies have demonstrated a positive association between HRT and breast cancer risk, but patient factors may influence the degree of risk, pointed out Ningqi Hou, MHS, PhD, of the University of Chicago in Chicago, Illinois, and colleagues in their report for Journal of the National Cancer Institute (2013;105[18]:1365-1372). To explore this relationship further, the team analyzed 1,642,824 screening mammograms, including 9,300 breast cancer cases, obtained from the National Cancer Institute’s Breast Cancer Surveillance Consortium. The patients were postmenopausal women aged 45 years and older.

Compared with nonusers of HRT, black women who used HRT had no increased risk for breast cancer. However, Asian women, Hispanic women, and white women who used HRT were at least 20% more likely to develop the disease.

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HRT use was associated with the highest breast cancer risk in women with low or normal BMI and extremely dense breasts, compared with nonusers. No excess risk of breast cancer was noted in overweight or obese HRT users with less-dense breasts.

Hou and coauthors concluded that black women, obese women, and women with breast tissue composed largely of fat may benefit from HRT with minimal excess risk for breast cancer. The investigators added that further studies are needed to confirm these findings and to provide more information on other modifiable risk factors for breast cancer in relation to HRT use.