Breast Cancer Risk Varies Among Women Taking Hormone Replacement

Hormone replacement therapy has been associated with an increased risk of breast cancer, but this risk varies depending on a woman’s race, body mass index (BMI), and breast density, according to the results of a study published early online in the Journal of the National Cancer Institute.

Breast cancer is the second leading cause of cancer death in women in the United States. The chance of an individual developing cancer depends on both genetic and non-genetic factors. Non-genetic factors may include diet, exercise, or exposure to other substances, including medications.

For many women, menopause has uncomfortable side effects such as hot flashes, sleep disturbances, depression, mood swings, and anxiety. Although hormone replacement therapy (HRT) has been widely prescribed for menopausal women, it has come under scrutiny because some studies have indicated that it may be associated with an increased risk of certain types of cancer, including breast cancer. Data has been widely conflicting and researchers continue to study the relationship between HRT and breast cancer. This latest study finds that the association between breast cancer and HRT may vary by patient factors.

Researchers used data from the Breast Cancer Surveillance Consortium to analyze nearly 1.65 million screening mammograms from postmenopausal women age 45 or older. They found that race, weight, and breast density played a role in the breast cancer risk associated with HRT.

HRT use was associated with more than a 20 percent increased risk of breast cancer in white, Asian, and Hispanic women—but not in black women. What’s more, women taking HRT who were considered underweight or normal weight (defined as a BMI under 25) had a 35 percent increased risk of breast cancer compared with those who did not use HRT. For obese women (BMI of 30 or higher), breast cancer risk did not appear to be affected by HRT use. Among women with extremely dense breasts, those who took HRT had a 40 percent increased risk of breast cancer compared with their counterparts who did not take HRT.

Women with a low or normal BMI and extremely dense breasts had the highest breast cancer risk associated with HRT compared with their counterparts who didn’t take HRT. In contrast, overweight or obese women with less dense breasts did not appear to have an increased risk associated with HRT.

The researchers concluded that the impact of HRT use on breast cancer risk varies according to race, BMI, and breast density. The speculate that this information could be helpful in terms of advising for or against HRT in menopausal women depending on their characteristics.


Hou N, Hong S, Wang W, et al. Hormone replacement therapy and breast cancer: Heterogeneous risks by race, weight, and breast density. Journal of the National Cancer Institute. Published early online September 3, 2013. doi: 10.1093/jnci/djt207

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