Results released in 2006 from the Women’s Health Initiative (WHI)—a large, randomized trial that studied the effects of hormone replacement therapy (HRT) in postmenopausal women—showed that taking estrogen and progestin increased the risk of breast cancer, blood clots and stroke, but also improved bone health and lowered colon cancer risks. In all, the balance showed no net benefit to using HRT for preventive health, but also little net risk for women choosing to use HRT to treat bothersome menopausal symptoms.
Additional analyses from the ongoing WHI study suggested that heart benefits might occur in women starting HRT in the immediate perimenopausal years. However, the breast cancer risks, though small, remain.
If severe menopausal symptoms (hot flashes, night sweats, disturbed sleep, decreased sex drive, vaginal dryness, discomfort or pain with intercourse) are disrupting your life and HRT may be the only treatment that provides effective symptom relief, how do you decide if it’s worth the risk?
Breast Cancer Risk: A Major Factor for Many
“When determining whether or not the potential risks of taking HRT outweigh the potential benefits, the most important factor is the patient’s own concerns,” says Margaret Polaneczky, MD, FACOG, associate professor of obstetrics and gynecology at Weill Cornell. “Women with menopausal symptoms who choose to use HRT can be reassured that the risks overall are small. However, I find most of my patients do not want even a very small increased risk of breast cancer, and many avoid even vaginal estrogen. I respect their choice and work with them to find non-hormonal solutions for their symptoms.”
Recent Findings
A meta-analysis (a review of numerous studies) published in September 2019 in The Lancet looked at the link between various types and timing of HRT regimens and breast cancer risk. Among study participants, duration of HRT use was between seven and 10 years, and mean age was 50 years at menopause and 50 years at starting HRT. Every type of HRT except use of vaginal estrogen was associated with higher breast cancer risks, which increased steadily as duration of use increased and were greater for estrogen-progestin than estrogen-only preparations.
“The study suggests that breast cancer risk when using HRT is slightly higher than the risk found in the WHI. I used to say, ‘If you use HRT for 20 years, your risks for breast cancer will be 1 percent higher.’ Now, I say the risk will be 1 to 2 percent higher,” explains Dr. Polaneczky.
“The study also supports the idea that estrogen alone rather than a combination of estrogen and progestin and intermittent rather than continuous progestin use carries less risk, so I discuss that with my patients when we are deciding which HRT regimen to use.
Weighing the Risks
HRT use dropped dramatically in response to the initial results of the WHI study, but the position taken by the North American Menopause Society, the American Society 
for Reproductive Medicine, and the Endocrine Society is that HRT is an acceptable treatment for menopausal symptoms. However, several factors must be taken into account when HRT use is being considered, including the patient’s current health, medical history, age, and the number of years since her menopause began.
Dr. Polaneczky stresses that each woman needs to have a thorough discussion with her doctor if she is considering HRT. “Depending on your age and other individual factors, the consequences of taking HRT can vary, and the benefits may outweigh the risks if you experience severe hot flashes or other intolerable menopausal symptoms that do not respond to non-hormonal treatments.”
If a woman does opt for HRT, she is advised to take the lowest effective dose for the shortest amount of time to minimize the increase in breast cancer, blood clot, and stroke risks. Dr Polaneczky also recommends that women use transdermal estrogens that are absorbed through the skin rather than oral estrogens when possible, as these may carry a lower risk for blood clot formation.
Dr. Polaneczky explains that it’s unlikely that she would recommend HRT if a patient has had breast cancer or coronary artery disease or is at risk for deep vein thrombosis (a blood clot in the leg), pulmonary embolism (a blood clot in the lungs), or stroke.
HRT Observations
The bottom line is that not much has changed since the initial WHI results were published.
“Women who choose to use HRT for symptom relief can be reassured that the breast cancer risks, while present, are less than one in 1,000 per year of use. If women choose to use HRT long term, they must accept an increased risk on the order of 1 to 2 percent over their baseline, but, in truth, most women stop using HRT once they get through the perimenopausal years and their symptoms diminish,” Dr. Polaneczky says.
If you do choose to use HRT, Dr Polaneczky recommends that you use an effective dose. “In my opinion, the worst outcome is women choosing to use HRT and accepting an increased risk of breast cancer and then not getting relief from their symptoms because they take a smaller dose than prescribed—or, even worse, they decide not to take the progestin I prescribe, which increases their risk of endometrial (uterine) cancer,” she explains.
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