Does HRT (Hormone Replacement Therapy) Increase Breast Cancer Risk?
Hormone replacement therapy (HRT), also known as menopause hormone therapy (MHT), is medicine that that replaces certain hormones that your body produces less of as you go through perimenopause and menopause. It’s used to ease menopausal symptoms such as hot flashes, insomnia, mood swings, and bone loss.
Most research suggests that the benefits of using HRT — such as improved quality of life and protection of bone health — outweigh the risks of these medicines for some people. If you have a history of breast cancer, however, most experts agree that taking certain types of HRT could increase your risk of breast cancer coming back (recurring).
“Having a detailed conversation with your doctors is important because the risks and benefits are going to vary tremendously from person to person depending on their health, risk for various diseases, menopausal symptoms, and the type of HRT they’re considering taking,” says Carol Fabian, MD, a breast medical oncologist and researcher who studies ways of addressing menopausal symptoms. Fabian is also director of the Breast Cancer Prevention and Survivorship Research Center at the University of Kansas Medical Center in Kansas City, KS.
What is hormone replacement therapy?
Hormone replacement therapy is hormonal medicine prescribed by a doctor.
There are two main types of HRT used to treat menopausal symptoms in people who are experiencing natural or surgically-induced menopause (removal of the ovaries):
estrogen-only HRT
combination HRT, which contains both estrogen and progesterone (usually a synthetic form called progestin or progestogen)
There are several ways that you can take or use HRT:
Systemic HRT is most often taken as a pill, although it can come in other forms such as skin patches, shots, implants, or creams. “Systemic” means the medicines travel through the bloodstream to all parts of the body. Systemic HRT effectively treats many symptoms of menopause, including hot flashes, night sweats, mood swings, and vaginal symptoms. In combination systemic HRT (containing both estrogen and progesterone), both hormones can either be combined into one medicine or given as separate medicines. Both hormones may be taken daily (called continuous HRT) or estrogen may be taken daily while progestin is taken for only part of each month (called sequential or cyclical HRT). Combination systemic HRT is usually taken by people who still have their uterus. This is because the progestin helps prevent overgrowth of cells lining the uterus, which can sometimes develop into endometrial or uterine cancer. Estrogen-only systemic HRT is usually taken by people who have had a hysterectomy (surgery to remove the uterus).
Vaginal estrogen, also sometimes called local HRT, contains low-dose estrogen. It comes in the form of creams, tablets, or rings applied or inserted into the vagina. These medicines mostly stay in the vaginal tissue, so only a small amount of estrogen is absorbed into the bloodstream. Vaginal estrogen improves vaginal symptoms, such as dryness and discomfort during sex, but not all menopausal symptoms. There are also local HRT medicines that contain other hormones called androgens, in particular DHEA, and that are used to treat vaginal symptoms.
What are the links between systemic HRT and breast cancer risk?
Here’s what’s important to know about systemic HRT (most often taken as a pill) and breast cancer risk.
In women with no history of breast cancer who are over the age of 50, combination HRT taken for five or more years slightly increases breast cancer risk, according to Women’s Health Initiative studies and other research. Whether this risk applies to all women with no history of breast cancer over the age of 50, or whether there are some groups that might not have any increased risk at all, is controversial. Many experts agree, though, that any increase in risk is likely to be small.
Higher-dose combination HRT increases breast cancer risk more than lower-dose combination HRT.
People who use combination HRT are more likely to develop dense breasts compared with people who don’t use combination HRT. Having dense breasts can make it harder for mammograms to detect breast cancer. Some research shows that women who take combination HRT are more likely to be called back to get extra mammogram images after an initial mammogram.
In women with no history of breast cancer, taking systemic estrogen-only HRT is not linked to a higher risk of breast cancer, according to the Women’s Health Initiative studies and other research. In certain groups of women, such as those who have no family history of breast cancer or benign breast disease, systemic estrogen-only HRT actually appears to lower the risk of breast cancer.
But it’s important to know that in women who have a uterus, using systemic estrogen-only HRT has been shown to increase the risk of an overgrowth of the cells lining the uterus — which can sometimes develop into endometrial or uterine cancer. (That’s why women who have a uterus are usually advised to use an IUD that releases progestin or to take systemic progestin in combination with systemic estrogen).
Many experts say that women with a history of breast cancer should not take any type of systemic HRT, especially if they have any breast tissue (for example, if they had a lumpectomy rather than a double mastectomy).
Because doctors are concerned that systemic HRT can cause breast cancers to develop, grow, or recur, 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 diagnosed with hormone receptor-positive breast cancer who took systemic HRT had an 80% higher risk of recurrence than those who didn’t take HRT. Most of the concern has focused on women who have had hormone receptor-positive breast cancer, although it’s often the case that women who have had any type of breast cancer are advised not to take systemic HRT.
Fabian notes that there is some research showing that in women who have had triple-negative breast cancer successfully treated in the past and had all their breast tissue removed (in a double mastectomy), taking systemic estrogen-only HRT won’t significantly increase their risk of recurrence. “I think estrogen replacement is safe for someone in that situation if they are several years from diagnosis and have no evidence of recurrence,” she says. “It’s especially worth considering if they were diagnosed with breast cancer at a young age and are having severe menopausal symptoms.”
Are there any links between vaginal estrogen and breast cancer risk?
Vaginal (also called topical) estrogen is the type of HRT that contains low-dose estrogen delivered as a ring, insert, or tablet in the vagina or as a cream applied to the vulva or vagina.
In women with no history of breast cancer, research suggests that vaginal estrogen doesn’t increase breast cancer risk because most of the hormones stay in the vaginal tissue.
In women who do have a history of breast cancer, vaginal estrogen is also generally considered safe. A 2023 study published in JAMA Oncology was one of several that showed that using vaginal estrogen doesn’t increase the risk of dying from breast cancer in people who’ve been diagnosed with breast cancer. The American College of Obstetricians and Gynecologists published guidelines in 2021 saying that women who’ve been diagnosed with breast cancer who are having troubling symptoms, such as pain during sex, may consider using low-dose vaginal estrogen if non-hormonal moisturizers or lubricants don’t work.
Are there any links between gender-affirming hormone therapy and breast cancer risk?
Transgender women and non-binary people assigned male at birth (amab) who take estrogen as a form of gender-affirming hormone therapy (GAHT) are at increased risk of breast cancer compared to cisgender men. After being on hormone therapy for 5 years, trans women and amab non-binary people aged 40 and up who are at otherwise average risk should receive annual mammograms.
Transgender men and non-binary people assigned female at birth (afab) who take testosterone as a form of gender-affirming hormone therapy have a lower risk of breast cancer than cisgender or transgender women but a higher risk than cisgender men.
What this may mean for you
If you're having severe hot flashes, vaginal dryness, or other menopausal side effects that are affecting your quality of life and you’re considering HRT, talk with your doctor about all of your options. Ask how you can relieve your symptoms while minimizing your breast cancer risk.
If you decide to take systemic combination HRT, two things that can help reduce the risk is taking it for the shortest time possible (for example, for less than three years) and at the lowest dose possible that is effective for you.
Also, keep in mind that the timing of when you start taking systemic combination HRT matters. The risk is higher if you begin taking it more than 10 years after the onset of menopause or when you’re more than 60 years old.
Some questions you may want to ask your doctor:
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?
Which type(s) of HRT, if any, would you recommend for me?
Would vaginal estrogen be a good option for me?
What other options are there — including non-hormonal medicines, complementary therapies, and lifestyle changes — to treat menopausal symptoms and osteoporosis?
Learn more about managing menopausal symptoms.
— Last updated on September 8, 2025 at 9:08 PM