Hormone Therapy for Breast Cancer

April 10, 2025

This page was reviewed under our medical and editorial policy by Hannah Chang, M.D., assistant professor, and Susan Yost, Ph.D., staff scientist, Department of Medical Oncology & Therapeutics Research, City of Hope^® Cancer Center Duarte

Hormone therapy is used to treat certain types of breast cancer. It is usually combined with other cancer treatments, but it may sometimes be given on its own.

Tests done on a tumor biopsy sample help patients and their care team know if breast cancer is hormone receptor (HR)-positive or HR-negative. As a cancer treatment, hormone therapy is recommended to treat hormone receptor-positive breast cancer by slowing its growth. This treatment may also reduce the likelihood that HR-positive cancer will return after treatment ends.

Some breast cancer tumors do not have these hormone receptors. Hormone therapy would not slow cancer growth in patients with this type of cancer, called hormone receptor-negative breast cancer.

Hormone therapy for breast cancer is also sometimes called endocrine therapy, anti-estrogen therapy or hormonal therapy. It is not the same as hormone replacement therapy used to treat menopause symptoms.

What Is Hormone Therapy for Breast Cancer?

Hormone therapy treatment may be recommended for HR-positive (HR+) breast cancer.

Some breast cancer cells have receptors (proteins) for the hormones estrogen and/or progesterone to attach to (or bind to). Breast cancers with binding sites are called HR-positive, and they may grow faster in the presence of estrogen or progesterone.

Hormone therapy is a tool to help prevent the body from producing estrogen and progesterone hormones or to block their effects, slowing cancer growth in hormone receptor-positive cancers. Hormone therapy helps to treat these HR+ cancerous cells throughout the body, not just in the breast.

HR status is typically included in a patient’s pathology report. Test results show whether cancer cells in the tissue sample contain hormone receptors (biomarkers) for either estrogen or progesterone. The report will also note the percentage of cancer cells with those receptors, as detailed below.

ER-positive (ER+) cancer: In this type of cancer, estrogen receptors are found in at least 1% of the cells in the tissue sample.

PR-positive (PR+) cancer: In this type of cancer, progesterone receptors are found in at least 1% of the cells in the tissue sample.

HR+ cancers may be positive for either estrogen (ER+) or progesterone (PR+) receptors — or both.

About 4 out of every 5 breast cancers are HR-positive. These cancers may benefit from hormone therapy.

Types of Hormone Therapy for Breast Cancer

A number of medications are used as breast cancer hormone therapy. Some are pills that a patient takes at home. Others are administered by injection in a health care setting. Four types of hormone therapy are used to treat breast cancer:

• GnRH (gonadotropin-releasing hormone) agonists
• Aromatase inhibitors
• SERMs (selective estrogen receptor modulators)
• SERDs (selective estrogen receptor degraders)

The type of medication chosen differs from patient to patient, depending on whether she has gone through menopause and if she may become pregnant.

Generally, a woman is considered in menopause when she has not had a menstrual period for 12 months. In some cases, a blood test is performed to confirm menopausal status.

For patients with uteruses who have not gone through menopause, a pregnancy test is recommended before starting hormone therapy to rule out any possibility of pregnancy. Their cancer care team may also discuss whether birth control is needed during hormone therapy treatment. For patients who might desire a future pregnancy, consultation with a fertility care provider is recommended to discuss fertility preservation options.

Stopping or Suppressing Ovarian Function

Before menopause, most estrogen in the body is made by the ovaries. Premenopausal women with breast cancer may benefit from treatments that stop or suppress estrogen production. Ovarian ablation is a process that shuts down the ovaries. This may be performed in several ways. One is by surgical removal of the ovaries (oophorectomy), which is permanent. Another is through hormone therapy.

Two types of medications are used for this purpose. Both are called GnRH agonists (or luteinizing hormone-releasing hormone — LHRH — agonists) because they both work like the body’s own estrogen-supporting brain chemical, also called gonadotropin-releasing hormone (GnRH) or luteinizing hormone-releasing hormone (LHRH). They are sometimes used along with other types of breast cancer hormone therapy. These medications are listed below.

Lupron Depot^® (leuprolide acetate): Leuprolide is a medication that mimics the effect of GnRH, which is normally released in pulses, by binding to its receptors. Leuprolide interrupts signals from the brain to the ovaries, which stops estrogen release and ovulation, as in natural menopause. Leuprolide is administered in a health care setting by injection into the muscle once a month (or every three months).

Zoladex^® (goserelin): Goserelin is another lab-made version of GnRH. It works the same way as leuprolide acetate, causing the ovaries to shut down. Goserelin is given as an injection just under the skin (subcutaneous) once every 28 days. Like leuprolide, it is administered in a health care setting.

Premenopausal women who are receiving ovarian ablation medications are put into a state of chemical menopause, which is usually temporary.

Ovarian suppression during cancer treatment is sometimes recommended for premenopausal women who might want to become pregnant in the future. Shutting down the ovaries may protect them from harmful effects of cancer treatment. However, this is not a proven method of fertility preservation. Patients interested in conceiving in the future should consult with a fertility expert before starting hormone therapy.

Stopping Estrogen From Being Produced

After menopause, the body’s main sources of estrogen are outside the ovaries in other parts of the body, including the adrenal glands, skin, muscle and, especially, in fat. At these locations, male sex hormones (androgens) are changed into estrogens. An enzyme called aromatase helps bring about this conversion.

Aromatase inhibitors are a type of hormone therapy used for HR-positive breast cancers. These medications block the enzyme aromatase, which stops most estrogen production. They are commonly recommended for postmenopausal women because they target estrogen from nonovarian sources.

While it is not safe for premenopausal women to take aromatase inhibitors without ovarian suppression, they are sometimes used along with ovarian suppression drugs in women with a higher risk of cancer recurrence.

Three aromatase inhibitor medications have approval from the U.S. Food and Drug Administration (FDA) for treating HR-positive breast cancer. They are:

• Arimidex^® (anastrozole)
• Femara® (letrozole)
• Aromasin^® (exemestane)

All are tablets taken by mouth once a day. Exemestane must be taken after meals, but anastrozole and letrozole may be taken with or without food.

Blocking Estrogen From Attaching to Cancer Cells

Another type of hormone therapy prevents estrogen in the body from binding to breast cancer cells that are fueled by estrogen. Two types of estrogen-blocking medications are used for breast cancer.

SERMs (selective estrogen receptor modulators): These drugs may be prescribed for both pre- and postmenopausal patients. They block estrogen receptors that tell breast cancer cells to grow and divide, and they have estrogen-like effects in other parts of the body, such as the uterus and bones. The FDA has approved two SERMs to treat breast cancer, oral tablets that may be taken with or without food:

• Soltamox^® (tamoxifen), taken once or twice daily (depending on dose)
• Fareston^® (toremifene), taken once daily

SERDs (selective estrogen receptor degraders): These medications also attach to estrogen receptors, but so tightly that receptors break down. They may also be used before or after menopause. However, SERDs should be combined with a GnRH agonist, also known as a LNRH agonist in patients who have not gone through menopause. They are:

• Orserdu^® (elacestrant), a pill taken by mouth once a day with food
• Faslodex^® (fulvestrant), an injection into muscle delivered by a health care professional who gives the first two doses two weeks apart, then patients receive monthly injections

How Is Hormone Therapy Used?

Hormone therapy is most often used along with other cancer treatments, which may include surgery, chemotherapy or radiation therapy (separately or at the same time). Hormone therapy treatment is usually given for at least five years. A Breast Cancer Index (BCI) score may be used to predict the benefit of continuing hormone therapy after that. This test is usually done on the biopsy sample at the time of diagnosis and helps the care team measure the likelihood of the cancer returning on its own.

Hormone therapy may be used at any time during cancer treatment for hormone receptor-positive cancers — and beyond.

After Surgery (Adjuvant)

After a breast cancer tumor is surgically removed, hormone therapy is often started to reduce the chance that the cancer will return. This type of hormone therapy is called adjuvant because it is started after breast cancer surgery.

The type and duration of hormone therapy recommended depends on whether the patient has gone through menopause. The care team will also consider their preferences, other risk factors and treatment tolerance.

Before menopause, some common hormone therapy regimens include:

• Tamoxifen for five to 10 years
• Tamoxifen for five years followed by an aromatase inhibitor for five years
• An aromatase inhibitor combined with ovarian suppression for five to 10 years

Examples of postmenopausal hormone therapy regimens include:

• Tamoxifen for two to six years followed by an aromatase inhibitor for up to five years
• Tamoxifen for five to 10 years
• An aromatase inhibitor for five to 10 years

Primary Treatment for Advanced or Metastatic Breast Cancer

Hormone therapy may also be beneficial for treating breast cancer that has returned or is diagnosed at an advanced stage. Types of hormone therapy that may be used to treat HR-positive advanced breast cancers include:

• Tamoxifen
• Aromatase inhibitors
• SERDs

In patients who have not gone through menopause, SERDs or aromatase inhibitors need to be combined with a GnRH (LHRH) agonist medication.

Before Surgery (Neoadjuvant)

Occasionally, hormone therapy is started before a breast cancer tumor is surgically removed. It is most often considered in postmenopausal women if chemotherapy is difficult for the patient to tolerate or if surgery has to be delayed. When hormone therapy is started before surgery, it is called neoadjuvant.

In Combination With Targeted Therapy

Hormone therapy is sometimes combined with targeted cancer therapy — medications targeting proteins that fuel the growth and survival of breast cancer cells. In some cases, a combined approach — hormone therapy plus targeted therapy for breast cancer — may make hormone therapy more successful.

Some targeted types of therapies that may be combined with hormone therapy:.

• CDK4/6 inhibitors — Verzenio^® (abemaciclib), Ibrance^® (palbociclib) and Kisqali^® (ribociclib)
• mTOR inhibitors — Afinitor^® (everolimus)
• PI3K inhibitors — Piqray^® (alpelisib) and Itovebi^® (inavolisib)
• AKT inhibitors — Truqap^® (capivasertib)

What to Expect From Hormone Therapy

Hormone therapy treatment for breast cancer typically continues for five to 10 years. The patient’s Breast Cancer Index (BCI) score is a tool used to indicate the need for hormone therapy for more than five years.

In the years after cancer is first diagnosed and treated, the initial treatment plan may change for many reasons. Sometimes, a cancer may progress, pointing to the need for a different hormone therapy medication. Other times, a patient’s preferences or other health conditions may prompt a change.

In between follow-up oncology visits, patients are encouraged to reach out to their care team with any concerns about their hormone therapy. In order for it to do its job, it must be taken consistently over time. If a patient is experiencing bothersome side effects, her care team may suggest options to manage them. They may also suggest alternative medications if appropriate.

Risks and Side Effects

Hormone therapy side effects are generally mild, but they may be bothersome for some patients. The most common types are menopause-like symptoms, such as:

• Hot flashes or night sweats
• Changes in menstrual cycle (premenopausal women)
• Vaginal dryness (or change in discharge)
• Muscle, bone or joint pain
• Mood changes
• Fatigue

Long-term hormone therapy may lower bone density, raising the risk for developing osteoporosis. A patient’s care team will discuss how to manage this risk over time. Bone density tests may be used to monitor a patient’s bone health, and bone-strengthening medications may be prescribed to reduce osteoporosis risk.

Hormone therapy may also increase levels of lipids in the blood. A patient’s care team will also monitor cholesterol levels before and during hormone therapy.

In addition to these side effects, each specific type of hormone therapy medication may have additional risks to consider. For example, SERDs are more likely to cause nausea. Injectable medications may cause a rash or irritation at the injection site.

Tamoxifen has some additional risks to know about. Patients with metastatic breast cancer may notice that their cancer symptoms worsen just after starting tamoxifen. This is called a “tumor flare.” This usually quickly resolves on its own, but patients should contact their care team for any severe or persistent symptoms. Rarely, more serious side effects may occur in people taking tamoxifen, including:

• Blood clots
• Cancer of the uterus
• Eye problems, including cataracts

Radiation Therapy Versus Hormone Therapy

Radiation therapy uses high-energy rays to destroy cancer cells directly in select areas, while hormone therapy deprives cancer cells in the breast and elsewhere of hormones that help them survive. Both are performed with the aim of getting rid of any cancer cells left behind after surgery. Radiation therapy for breast cancer after patients have healed from surgery (and any chemotherapy is over) has been shown to be an appropriate treatment option after breast-conserving surgery to help prevent cancer from coming back.

Radiation therapy and hormone therapy each carry different side effects. Radiation therapy may cause short and more serious long term side effects, while hormone therapy is a longer term commitment that some patients may struggle to comply with.

Hormone therapy may be taken at the same time as radiation therapy, but some patients with early-stage HR+ breast cancer may choose between hormone therapy and radiation therapy after surgery. For example, the National Comprehensive Cancer Network (NCCN) endorses hormone therapy alone after surgery for women over age 70 with HR+ early-stage breast cancer, rather than adjuvant radiation therapy.

Choosing between these two therapies after surgery may be an option for some patients.

Researchers continue to look at which patients benefit from radiation therapy or hormone therapy after surgery, alone or in combination, to improve survival.

Treatment approaches are based on many factors, such as:

• Type of cancer, including the hormone receptor status biomarker
• How quickly the cancer may grow
• How likely the cancer is to spread to other parts of the body (metastasize)
• How likely a treatment is to work and how it may be tolerated
• Likelihood that a tumor may grow back

Other factors are also considered, including the patient’s overall health, any other medical conditions and preferences. The cancer care team helps to guide a patient and her loved ones through the decision-making process.

Chemotherapy Versus Hormone Therapy

Chemotherapy works by destroying fast-growing cells, like cancer cells, throughout the body, while hormone therapy stops these cells from binding to hormones that help them survive and multiply. Both are appropriate, systemic treatments for breast cancer.

Hormone therapies treat HR+ breast cancers, including very early-stage breast cancer called ductal carcinoma in situ (DCIS).

Chemotherapy for breast cancer typically is not used to treat DCIS, and it is most often recommended for patients with invasive or metastatic breast cancer, regardless of hormone status. Chemotherapy may be given before surgery (neoadjuvant) or after (adjuvant).

Treatment choices hinge on many factors. To recommend chemotherapy and/or hormone therapy, the cancer care team considers a patient’s:

• Age and menopause status
• Hormone receptor status
• HER2 status
• Results of gene expression tests
• Tumor type (size, grade and growth rate)
• Likelihood of tolerating treatment
• Overall health

Chemotherapy side effects may be bothersome and have long-term impacts. Researchers are investigating whether other therapies, like hormone therapy, may be utilized more in cancer care with the same or improved survival.

Some patients with smaller HR+ breast cancers may be able to choose reduced or even no chemotherapy when hormone therapies are followed. This is an individual decision, guided by the patient’s cancer care team after looking at many patient factors.

In addition to chemotherapy and hormone therapy, other types of cancer medications that may be included in a patient’s treatment plan include immunotherapy, targeted drug therapy and HER2 therapy.

The cancer care team will help a patient and their loved ones through the decision-making process.