Hormone therapy can help block the production of specific hormones that help some types of breast cancer grow. Doctors may recommend using it with other treatments, such as chemotherapy and radiation.

Hormone therapy, also known as endocrine therapy, can treat some types of breast cancer. Doctors commonly combine it with other treatments, such as surgery, radiation, or chemotherapy, if needed.

Breast cancer treatment aims to shrink and eradicate tumors as well as prevent future tumor growth.

Read on as we explore the different types of hormone therapy, when it’s an option, and what you can expect with this treatment.

There are many types of breast cancer. If your cancer tests positive for estrogen receptors (ER) or progesterone receptors (PR), that means it’s using these hormones to grow and potentially spread.

Hormone therapy drugs help block production or stop these hormones from attaching to the hormone receptors (HR). These drugs are used as an active treatment to shrink, control, and destroy cancer cells. They can also lower the chance of recurrence.

About 75% of breast cancers are HR-positive.

Doctors may also recommend certain drugs, such as tamoxifen, for people who don’t have breast cancer but have a high risk of developing it. This is commonly called chemoprevention. It may help lower the chances of breast cancer developing in the first place.

Hormone therapy for breast cancer is not the same as hormone replacement therapy (HRT) used for menopause.

Hormone therapy is only effective for HR-positive tumors. If your breast cancer tumor is HR-negative, your oncologist will recommend other treatments.

Doctors typically recommend hormone therapy in premenopausal or postmenopausal females with any stage of HR-positive breast cancer.

Hormone therapy that starts before surgery or radiation treatment is called neoadjuvant therapy. This can help shrink the tumor and make surgery easier.

When you begin hormone therapy treatment after surgery or radiation, it’s called adjuvant therapy. The goal here is to lower the risk that your cancer will spread or come back.

Some people with HR-positive breast cancer may only need hormone therapy. Doctors can order tests to evaluate the tumor’s genetics to determine whether to recommend chemotherapy.

According to the American Cancer Society (ACS), hormone therapy usually lasts at least 5–10 years but can vary depending on individual factors as well as the type of therapy.

Our bodies make a variety of hormones that help control how certain cells work.

The hormones estrogen and progesterone are mainly produced in the ovaries of premenopausal females. They’re also produced in other tissues, so postmenopausal females and males have some estrogen and progesterone.

These hormones can also promote the growth of some breast cancers.

Treatments like surgery and radiation target specific areas of the body, such as the tumor site or lymph nodes. They’re considered localized treatments because they focus on very specific areas.

Hormone therapies, on the other hand, are considered systemic treatments because they target hormones throughout the body.

Each type of hormone therapy has its own mechanism of action. They may help stop or slow growth or prevent recurrence by blocking:

  • ovarian function
  • estrogen production
  • estrogen effects

Doctors use several types of hormone therapy to treat breast cancer, including:

Selective estrogen receptor modulators

Also called SERMs, these drugs prevent breast cancer cells from binding to estrogen. SERMs block the effects of estrogen in breast tissue but not in other tissues within the body.

Traditionally, these drugs are usually used to treat breast cancer in premenopausal females. The most commonly used SERMs include:

  • Tamoxifen (Soltamox): This medication blocks estrogen from binding to estrogen receptors on breast cancer cells. This helps stop the cancer from growing and dividing. People who take tamoxifen for 10 years following breast cancer treatment are less likely to have the cancer return and more likely to live longer than people who took the drug for only 5 years, according to the National Cancer Institute.
  • Toremifene (Fareston): This drug, which isn’t commonly used in the United States, is only approved to treat HR-positive breast cancer that’s spread to other parts of the body in postmenopausal females. It may not be beneficial for people whose cancer has had a limited response to tamoxifen.

Side effects of selective estrogen receptor modulators

Tamoxifen and other SERMs can cause:

These medications may also increase your risk of blood clots and endometrial cancer, but these side effects are rare. In some cases, tamoxifen can cause stroke and may increase your risk of a heart attack.

Selective estrogen receptor degraders

Also called SERDs, these drugs bind tightly to estrogen receptors and cause them to break down. SERDs can block the effects of estrogen in breast tissue and in the rest of the body.

Doctors typically recommend them to people who have already gone through menopause. If a doctor recommends them for a premenopausal person, they typically need to be prescribed along with a luteinizing hormone-releasing hormone (LHRH) agonist to suppress the ovaries.

  • Fulvestrant (Faslodex): This is an injectable ER-blocking medication that’s commonly used to treat advanced breast cancer. Unlike other SERMs, it blocks the effect of estrogen throughout the entire body. Fulvestrant is often used with other drugs such as palbociclib (Ibrance).
  • Elacestrant (Orserdu): This is an oral medication that’s taken daily. Doctors use it to treat advanced, ER-positive, HER2-negative breast cancer with an ESR1 gene mutation.

Side effects of selective estrogen receptor degraders

Fulvestrant and other SERDs can cause:

  • hot flashes
  • headache
  • nausea
  • fatigue
  • appetite loss
  • pain in the muscles, joints, or bones
  • increased blood cholesterol and blood lipid levels (elacestrant)

Aromatase inhibitors

Aromatase inhibitors prevent the production of estrogen from fat tissue but have no effect on the estrogen the ovaries produce.

Since they can’t stop ovaries from producing estrogen, aromatase inhibitors are only effective if you have already gone through menopause. They’re approved for postmenopausal females with any stage of ER-positive breast cancer.

In premenopausal females, an aromatase inhibitor combined with ovarian suppression is more effective than tamoxifen in preventing breast cancer recurrence after initial treatment. It’s now considered the standard of care.

Common aromatase inhibitors include:

Side effects of aromatase inhibitors

Side effects of these medications include:

Estrogen is important for bone development and strength, and aromatase inhibitors can limit natural estrogen production. Taking them may increase your risk of osteoporosis and bone fractures.

Ovarian ablation or suppression

For females who have not gone through menopause, ovarian ablation may be an option. This can be done medically (called chemical menopause) or surgically. Either method stops estrogen production, which can help inhibit the growth of cancer.

Surgical ablation is done by removing the ovaries. Without the production of estrogen from the ovaries, you enter permanent menopause.

Symptoms of menopause may include:

  • hot flashes
  • vaginal dryness
  • changes in sex drive
  • mood changes

Luteinizing hormone-releasing hormones

Drugs called luteinizing hormone-releasing hormones (LHRH) can be used to stop the ovaries from producing estrogen altogether. This is known as chemically induced menopause.

These drugs include goserelin (Zoladex) and leuprolide (Lupron).

Ovarian suppression drugs will cause temporary menopause. Healthcare professionals will likely also prescribe an aromatase inhibitor for people who choose this option.

Hormone therapy is quite successful for most people with HR-positive breast cancer. It can also prolong life and reduce cancer-related symptoms in people with metastatic or late-stage HR-positive breast cancer.

A 2017 review of clinical trials found that hormone therapies have significantly decreased cancer-related deaths. Researchers wrote that these therapies have revolutionized breast cancer treatment.

Research published in 2019 suggests that the duration of hormone treatment matters a great deal. Study authors found that people who had fewer than 2 years of therapy showed the lowest survival rate.

Research from 2023 suggests that for some people with early HR-positive breast cancer, pausing hormone therapy after 2 years to become pregnant may be safe.

According to the ACS, the overall 5-year average survival rate for breast cancer, based on people diagnosed with breast cancer between 2012 and 2018, is:

  • localized: 99%
  • regional: 86%
  • distant: 30%

Note that these numbers are based on averages and do not take into account individual factors that can contribute to a person’s outlook, including age, overall health, specific mutations, tumor grade, treatment options, or their response to treatment.

Your oncologist can provide a more specific life expectancy that takes these factors into account.

Hormone therapy is an effective treatment for people with HR-positive breast cancer. It works by blocking production or stopping hormones from fueling the breast cancer.

There are several types of hormone therapies. Menopausal status is one factor that will help your doctor determine which therapy is right for you.

Hormone therapy reduces the risk of breast cancer recurrence in females with HR-positive breast cancer. If you have breast cancer, talk with your oncologist about whether you may benefit from hormone therapy.