Hormone replacement therapy (HRT), or taking estrogen and progestin to relieve hot flashes and night sweats, used to be standard practice for postmenopausal women (the treatment was all the more popular because it was thought to reduce heart disease risk as well). But in 2002, the results of one study changed that nearly overnight.
The Women’s Health Initiative (WHI) was a large, long-term series of clinical trials and studies, sponsored by the National Institutes of Health, to study a wide range of health issues facing postmenopausal women. One of the trials was designed to look at whether hormone therapy would decrease the risk of heart disease and osteoporosis.
In 2002, the NIH stopped this trial early because of findings showing that HRT did not reduce heart attack risk and actually raised the risk of stroke. Worse, they found a 24 percent increase in breast cancer risk for women taking estrogen and progestin together. By 2003, prescriptions for HRT had fallen 38 percent.Yet it’s not clear whether all women face the same risk. Subsequent research has shown differences among age, race and body type, and a new study led by Dezheng Huo, PhD, assistant professor of epidemiology in the Department of Health Studies at the University of Chicago, found that for some women, hormone replacement therapy might still provide a benefit without added risk for breast cancer.
Huo and his colleagues analyzed more than 1.6 million screening mammograms and 9,300 breast cancer cases in postmenopausal women 45 years and older, and considered their ethnicity, body mass index (BMI) and breast density. The study was published in the Journal of the National Cancer Institute.
Greater breast density means a woman has more breast tissue and connective tissue than fat; lower breast density means they have a relatively higher percentage of fatty tissue. Women with extremely dense breasts have a greater risk for breast cancer overall.
In this study, the researchers found that HRT was linked to an increased risk for breast cancer in white, Asian and Hispanic women, but not in African American women. The highest risk was seen in women with low to normal BMI and extremely dense breasts, who were almost 50 percent more likely to develop breast cancer while taking HRT.
Women who were overweight—i.e. had a higher BMI—and had less dense breasts, about 20 percent of the study population, had no increased risk. Huo said this means there is a large population of women who could still benefit from HRT with no additional risk of developing breast cancer if HRT is used for a short period of time.
“I truly believe that we cannot just give a medication to somebody without considering their basic characteristics. We should take that into account,” he said. “Hopefully doctors can take this result into consideration when they consider prescribing HRT to a patient to treat their menopausal symptoms.”
Hou N., Hong S., Wang W., Olopade O.I., Dignam J.J. & Huo D. (2013). Hormone Replacement Therapy and Breast Cancer: Heterogeneous Risks by Race, Weight, and Breast Density, JNCI Journal of the National Cancer Institute, 105 (18) 1365-1372. DOI: 10.1093/jnci/djt207