Using HRT (Hormone Replacement Therapy) – breast cancer

Hormone replacement therapy (HRT) also called estrogen replacement therapy, menopausal hormone therapy, or post-menopausal hormone therapy can be an effective treatment for menopausal symptoms, but its important to know that some types of HRT can increase your risk of breast cancer.

HRT also can increase your risk of the cancer coming back (recurrence) if youve been diagnosed with breast cancer in the past. Because of this risk, doctors usually recommend that women with a history of breast cancer should not take types of HRT that affect the entire body (called systemic HRT).

HRT has also been linked to cardiovascular risks, such as heart disease, stroke, and blood clots.

However, all of these risks vary and depend on many factors, including:

type of HRT

the dose you take

your age when you start taking it

how long you use it

Years ago, before the link between HRT use and breast cancer risk was known, many women took HRT for years to ease menopausal symptoms and prevent bone loss. After 2002, when research linked HRT and breast cancer risk, the number of women taking HRT dropped dramatically.

Newer research that has followed women for a longer amount of time suggests the link between HRT and breast cancer risk is more complex than first thought, and using HRT remains a controversial topic.

Medical guidelines say the benefits of HRT such as quality of life and protection of bone health can outweigh the risks for certain women, particularly those who enter menopause at an early age. Because the risks and benefits are different for every woman, its best to educate yourself and talk with your doctor to decide if HRT is right for you.

HRT medicines usually contain the hormones estrogen, progesterone, or both, to replace the hormones a womans body stops making after menopause.

HRT is different than hormonal therapy medicines that block estrogen to treat hormone receptor-positive breast cancer.

There are two main types of HRT:

estrogen-only HRT

combination HRT, which contains both estrogenand progesterone (usually a synthetic form called progestin or progestogen)

Estrogen-only HRT usually is taken only by women who have had a hysterectomy (surgery to remove the uterus).

Combination HRT usually is taken by women who still have their uterus. Estrogen-only HRT can cause the lining of the uterus to become too thick a condition called estrogen-associated endometrial hyperplasia. This can increase the risk of cancer of the uterus, called endometrial or uterine cancer. The progesterone in combination HRT helps to prevent thiscondition.

In combination HRT, both hormones can either be combined into one medicine or given as separate medicines. The same dose of estrogen and progesterone can be taken daily (continuous HRT), or in different amounts on different schedules (sequential or cyclical HRT).

There are several ways to take or use HRT:

Systemic HRT usually contains a higher dose of estrogen and comes in many forms, including pills, skin patches, creams, gels, sprays or vaginal rings. Systemic means the medicines travel through the bloodstream to all parts of the body.

Topical (local) HRT contains a lower-dose of estrogen and comes in the form of creams, tablets, or rings applied or inserted into the vaginal area. These medicines arent as readily absorbed into your bloodstream and mostly stay in the vaginal tissue.

Systemic HRT effectively treats many symptoms of menopause, including hot flashes and night sweats. Topical HRT only works on vaginal symptoms, such as dryness and discomfort during sex.

Breast cancer risk differs depending on the type of HRT and a womans personal history of breast cancer.

Systemic combination HRT and breast cancer risk in women with no history of breast cancer

Based on results from the very large Womens HealthInitiative studies, combination HRT increases breast cancer risk and this increase in risk lasted for more than 10 years after the women stopped taking HRT.

Higher-dose combination HRT increases breast cancer risk more than lower-dose combination HRT.

Combination HRT also increases the likelihood that the cancer may be found at a more advanced stage. Combination HRT is linked to increased breast density, which can make it harder for mammograms to detect breast cancer.

Breast cancer risk appears to be higher with daily progesterone (continuous combination HRT) than with less frequent progesterone (sequential or cyclical combination HRT).

This increase in risk applies to bioidentical and natural hormone products as well as synthetic hormones. Bioidentical means the hormones in the product are identical to the hormones your body produces. Bioidentical hormones are derived from plants, so theyre sometimes called natural. Synthetic hormones are made in a lab and are also chemically identical to thehormones in your body. It's important to know that many herbal and bioidentical HRT products fall outside the jurisdiction of the United States Food and Drug Administration and so aren't subject to the same regulations and testing that medicines are.

Systemic estrogen-only HRT and breast cancer risk in women with no history of breast cancer

The American Cancer Society says estrogen-only HRT is not linked to a higher risk of breast cancer. The Womens Health Initiative studies also found no increase in breast cancer risk in women using systemic estrogen-only HRT.

But its very important to know that in women who have a uterus, using systemic estrogen-only HRT has been shown to increase the risk of endometrial cancer. Other studies have found a link between systemic estrogen-only HRT and a higher risk of ovarian cancer.

Its also important to know that research is conflicting when it comes to breast cancer risk and estrogen-only HRT. Some studies show a small increase in risk, and some dont.

Any type of systemic HRT and breast cancer risk in women with a history of breast cancer

Because doctors are concerned that systemic HRT can cause hormone receptor-positive breast cancer to come back, only a few studies have been done on HRT use in women with a history of breast cancer. A 2021 analysis of four studies found that women who took systemic HRT had a 46% higher risk of recurrence than women who didnt take HRT. Current recommendations say that women with a history of breast cancer should not take any type ofsystemic HRT.

Topical HRT and breast cancer risk in women with no history of breast cancer

Research suggests that topical HRT, such as low-dose vaginal estrogen creams, tablets, and rings do not increase breast cancer risk because most of the hormones stay in the vaginal tissue.

Topical HRT and breast cancer risk in women with a history of breast cancer

In 2016, the American Congress of Obstetricians and Gynecologists concluded that women whove been diagnosed with breast cancer who are having troubling systems such as pain during sex may consider using vaginal estrogen at the lowest effective dose if non-hormonal moisturizers or lubricants dont work.

Menopausal side effects can reduce quality of life for some women. You have to weigh the benefits of HRT against the risks.

If you're having severe hot flashes or other menopausal side effects and are considering HRT, talk to your doctor about all of your options. Ask how you can relieve your symptoms while minimizing your breast cancer risk. Some questions you may want to ask:

What is my personal risk of breast, ovarian, endometrial, and other types of cancer? How will this risk be affected by HRT?

What is my personal risk of other conditions that HRT can affect, such as heart disease and stroke?

What other options are there including non-hormonal medicines and complementary therapies to treat menopausal symptoms and osteoporosis?

Would topical HRT be a good option for me?

Learn more about Treating Menopausal Symptoms.

Poggio, F., Del Mastro, L., Bruzzone, M. et al. Safety of systemic hormone replacement therapy in breast cancer survivors: a systematic review and meta-analysis. Breast Cancer Res Treat (2021). https://doi.org/10.1007/s10549-021-06436-9

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Using HRT (Hormone Replacement Therapy) - breast cancer