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​Hormone therapy

If you’ve been diagnosed with breast, endometrial or prostate cancer, your cancer team may recommend hormone therapy as part of your treatment plan. You likely have lots of questions about this type of treatment, its advantages and its potential downsides.

Also referred to as hormonal or endocrine therapy, this cancer treatment is different from menopausal hormone replacement therapy (HRT), which refers to the prescription of supplemental hormones to help relieve the symptoms of menopause.

Certain cancers rely on hormones to grow. In these cases, hormone therapy may slow or stop their spread by blocking the body’s ability to produce these particular hormones or changing how hormone receptors behave in the body. 

Breast and prostate cancers are the two types most commonly treated with hormone therapy. Most breast cancers have either estrogen (ER) or progesterone (PR) receptors, or both, which means they need these hormones to grow and spread. By contrast, prostate cancer needs testosterone and other male sex hormones, such as dihydrotestosterone (DHT), to grow and spread. Hormone therapy may help make these hormones less available to growing cancer cells.

Hormone therapy is available via pills, injection or surgery that removes hormone-producing organs, namely the ovaries in women and the testicles in men. It’s typically recommended along with other cancer treatments.

If hormone therapy is part of your treatment plan, discuss potential risks or side effects with your care team so that you know what to expect and can take steps to reduce them. Let doctors know about all your other medications to avoid interactions.

Types of hormone therapy for breast cancer

Aromatase inhibitors

Aromatase inhibitors—such as anastrozole (Arimidex®), letrozole (Femara®) and exemestane (Aromasin®)—work by inactivating aromatase, which your body uses to make estrogen in the ovaries and other tissues.

When and why they’re used: These medications are used primarily in women who have gone through menopause. Estrogen production declines dramatically after menopause. Premenopausal women produce too much aromatase for the inhibitors to work effectively. (Aromatase inhibitor drugs may be prescribed for younger women if they’re given with a drug to suppress ovarian function.)

Ask your care team whether you may benefit from aromatase inhibitors based on your cancer’s characteristics. Patients may receive aromatase inhibitors before surgery to shrink tumors for easier removal, or after treatment to prevent breast cancer from returning. These drugs may also play a role in breast cancer prevention for certain people who are at high risk.

Risks: While side effects differ based on the type of hormone therapy, the main ones in women with all types of hormone therapy (including aromatase inhibitors) are:

  • Hot flashes
  • Night sweats
  • Vaginal dryness or atrophy

These are similar to symptoms of menopause, as both hormone therapy and menopause reduce the amount of estrogen in the body. In relatively rare instances, aromatase inhibitors may also increase the risk for heart attack, chest pain (angina), heart failure, high cholesterol, bone loss, joint pain, depression and mood swings.

Selective estrogen receptor modulators (SERMs)

Selective estrogen receptor modulators (SERMs)—including tamoxifen (Nolvadex®), raloxifene (Evista®) and toremifene (Fareston®)—selectively block estrogen from certain tissues, namely the breast, while increasing its availability in other areas such as the bones.

When and why they’re used: Doctors may recommend SERMs after surgery for early ER-positive breast cancer in men or women, to reduce the chances that it recurs. They’re also approved to treat advanced breast cancer, and may be used to prevent breast cancer in high-risk individuals. Toremifene is only approved for advanced stage breast cancer that has spread.

Risks: In addition to more common side effects of hormone therapy such as hot flashes, tamoxifen risks may include blood clots, stroke, bone loss, mood changes, depression and loss of sex drive. Men who take tamoxifen may experience headaches, nausea, vomiting, rashes, impotence and loss of sex drive. Raloxifene may increase a patient’s chances of having a stroke or developing potentially fatal blood clots in the lungs or legs. Fortunately, these side effects are considered relatively rare. Have your doctor explain the potential side effects associated with each SERM when discussing the pros and cons of these medications with you.

Fulvestrant (Faslodex)

Fulvestrat binds to estrogen receptors, completely stopping the hormone from attaching to the receptors.

When and why it’s used: Fulvestrant is approved for women who have advanced ER-positive breast cancer that has spread following treatment with other types of hormone therapy. It’s also prescribed for postmenopausal women with ER-positive, HER2-negative cancers (meaning they have normal levels of human epidermal growth factor receptor-2) who have not undergone other hormone therapy.

Risks: Fulvestrant may cause nausea, vomiting, constipation, fatigue, back pain, bone pain, joint pain, headaches, hot flashes and breathing issues.

Ovarian suppression

Ovarian suppression may involve surgery, drugs or radiation therapy.

The surgical procedure, called an oophorectomy, removes the ovaries to stop them from producing estrogen, while drugs prescribed for this purpose include gonadotropin releasing hormone (GnRH) analog and luteinizing hormone-releasing hormone (LHRH) analog.

When and why they’re used: These types of therapies may be recommended with either tamoxifen or an aromatase inhibitor for premenopausal patients.

Risks: Ovarian suppression may cause bone loss, mood swings, depression and loss of libido, along with hot flashes, night sweats, and vaginal dryness or atrophy.

Types of hormone therapy for prostate cancer

Hormone therapy may be part of prostate cancer treatment if the cancer has spread and can’t be cured by surgery or radiation therapy—or if the patient isn’t a candidate for these other types of treatment. It may also be recommended if cancer remains or returns after surgery or radiation therapy, or to shrink the cancer before radiation therapy.

Additionally, hormone therapy may be combined with radiation therapy initially if there’s a high risk of cancer recurrence. It can also be given before radiation therapy to shrink the cancer and make other treatments more effective. Other types of hormone therapy for prostate cancer include:

Androgen deprivation therapy (ADT)

This type of therapy includes LHRH agonists, also called LHRH analogs or GnRH agonists,  such as Leuprolide (Lupron®, Eligard®), Goserelin (Zoladex®), Triptorelin (Trelstar®) or Histrelin (Vantas®).

When and why they’re used: Intended to lower the amount of testosterone produced by the testicles, these drugs are injected or placed as a small implant under the skin. Doctors may refer to this as “medical castration.” Orchiectomy or surgical castration is the removal of the testicles.

Risks: Side effects may include:

  • Lack of sexual interest
  • Shrinkage of testicles and penis
  • Hot flashes
  • Breast tenderness
  • Growth of breast tissue
  • Bone thinning and fractures
  • Low red blood cells (anemia)
  • Brain fog
  • Loss of muscle mass
  • Weight gain
  • Fatigue
  • High cholesterol
  • Depression

These drugs sometimes cause an initial increase in male sex hormones, which may be dangerous. LHRH antagonists are another type of androgen deprivation therapy that doesn’t cause this initial rise or flare. Both LHRH agonists and antagonists may stop the testicles from making androgens but don’t control production in other parts of the body, such as the adrenal glands. This means that a tumor may still have access to the hormones it needs to grow. Drugs are available that block androgen made by cells outside of the testicles.

Androgen blockers

These pills prevent male sex hormones from promoting tumor growth.

When and why they’re used: Doctors may suggest androgen blockers if an orchiectomy or an LHRH agonist or antagonist is no longer working. (An anti-androgen is also sometimes prescribed for a few weeks when an LHRH agonist is first started to prevent a possible flare.)

Newer anti-androgens, available as daily pills, include enzalutamide (Xtandi®), apalutamide (Erleada®) and darolutamide (Nubeqa®).

Risks: Side effects may include diarrhea, fatigue, rash and worsening hot flashes. Dizziness and seizures are more severe, but less common, side effects.

Estrogens may be tried for prostate cancer if other hormone treatments are no longer working.

Hormonal therapy for endometrial cancer

Cancer of the uterus or its lining, the endometrium, may respond to hormone therapy with progestins. Other types of hormone therapy for endometrial cancer include:

  • Tamoxifen
  • LHRH agonists
  • Aromatase inhibitors

When and why they’re used: Hormone therapy is typically reserved for advanced uterine or endometrial cancer, or for cancer that has returned after treatment. It’s often combined with chemotherapy.

Risks: Side effects are similar to those seen with hormone treatment for other types of cancer.

The information on this page was reviewed and approved by
Maurie Markman, MD, President, Medicine & Science at CTCA.

This page was updated on May 24, 2021.