The short answer
Hormone therapy slows or stops the growth of breast cancers that use hormones to grow. It helps people whose cancer is hormone receptor positive. Types include drugs that block or lower estrogen. Common side effects are hot flashes, night sweats, and loss of interest in sex.
Hormone therapy is used for breast cancers that are hormone receptor positive (HR positive).
About 80% of people diagnosed with breast cancer have HR-positive cancers.
It works by blocking the body's ability to make hormones or by blocking hormones' effects on cancer cells.
It may be given before surgery, after surgery, or for advanced or recurrent cancer.
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The full explanation.
The simple version
Some breast cancers use hormones to grow. Hormone therapy (also called hormonal therapy, hormone treatment, or endocrine therapy) slows or stops the growth of these tumors. It does this by blocking the body's ability to produce hormones or by interfering with the effects of hormones on breast cancer cells.
Hormone therapy works against breast cancers that rely on hormones to grow.
Who it helps
You may receive hormone therapy if the cells in your breast cancer contain proteins called hormone receptors. There are two kinds: estrogen receptors (ERs) and progesterone receptors (PRs). To find out, doctors test samples of tumor tissue removed by surgery.
If the tumor cells contain hormone receptors, the cancer is called hormone receptor positive (HR positive). Tumors that lack them (HR negative) do not respond to hormone therapy. About 80% of people diagnosed with breast cancer have HR-positive cancers.
Hormone therapy for breast cancer is different from menopausal hormone therapy.
The main types
Your doctor may suggest one or more types depending on your menopausal status, desire to preserve fertility, and stage of disease.
Therapies that block ovarian function. Before menopause, the ovaries are the main source of estrogen. Blocking ovarian function (called ovarian ablation) can reduce or remove estrogen. This can be done permanently with surgery or radiation, or temporarily with drugs that interfere with the signals that tell the ovaries to make estrogen.
Aromatase inhibitors. These block an enzyme called aromatase, which the body uses to make estrogen. They are used mainly in postmenopausal women, though premenopausal women can take them together with a drug that suppresses ovarian function.
Therapies that block estrogen's effects. Two kinds of drugs interfere with estrogen's ability to fuel cancer growth:
- Selective estrogen receptor modulators (SERMs) bind to estrogen receptors. In breast cells, they block estrogen's effects. Tamoxifen is used in both premenopausal and postmenopausal women; toremifene is used only in postmenopausal women.
- Selective estrogen receptor degraders (SERDs) bind strongly to estrogen receptors and also destroy them. Fulvestrant is a SERD used only in postmenopausal women.
How it is used
Hormone therapy for HR-positive breast cancer may be given after surgery (adjuvant therapy) or before surgery (neoadjuvant therapy). It can also be used if your disease is HR positive but cannot be treated with surgery, if the cancer has come back, or if it is advanced or metastatic.
- Adjuvant therapy for early-stage cancer. After surgery, hormone therapy can reduce your risk of new or recurrent breast cancer. Tamoxifen, aromatase inhibitors, and ovarian suppression may all be used.
- Neoadjuvant therapy. Postmenopausal women who cannot take chemotherapy or cannot have surgery right away may receive aromatase inhibitors before surgery.
- Advanced, metastatic, or recurrent cancer. Several types of hormone therapy are approved for these situations. Some people are treated with a combination of hormone therapy and targeted therapy.
Side effects and effectiveness
The side effects depend on the specific drug. The most common are hot flashes, night sweats, and loss of interest in sex. Hormone therapy may also disrupt the menstrual cycle in premenopausal women.
If side effects interfere with your life, many can be relieved by switching therapies or adjusting your dose. One common approach is to take tamoxifen for 2 or 3 years, then switch to an aromatase inhibitor. Stopping or refusing hormone therapy is your decision, but research shows it can effectively lower your risk of new and recurrent breast cancer and of dying from breast cancer.
Studies over many decades show that hormone therapy, when taken for 5 years or more, can greatly reduce the risk of new breast cancer, recurrence, and death from breast cancer. Some medicines, including certain antidepressants, can reduce how well tamoxifen works, so tell your doctor about all the medicines and supplements you take.
Taken over several years, hormone therapy can meaningfully lower the chance that HR-positive breast cancer returns.
Words to know
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Common questions
▸Who gets hormone therapy for breast cancer?
You may receive hormone therapy if your breast cancer cells contain proteins called hormone receptors — estrogen receptors (ERs) or progesterone receptors (PRs). If the cells have them, the cancer is called hormone receptor positive. Tumors without them (HR negative) do not respond to hormone therapy. About 80% of people diagnosed with breast cancer have HR-positive cancers.
▸How does hormone therapy work?
Hormone therapy slows or stops the growth of some breast tumors by blocking the body's ability to produce hormones or by interfering with the effects of hormones on breast cancer cells.
▸What are the main types of hormone therapy for breast cancer?
Types include therapies that block ovarian function, aromatase inhibitors that block estrogen production, and drugs that block estrogen's effects — such as selective estrogen receptor modulators (SERMs) like tamoxifen and selective estrogen receptor degraders (SERDs).
▸When is hormone therapy given?
Hormone therapy may be given after surgery (adjuvant therapy) to lower the risk of the cancer returning, or before surgery (neoadjuvant therapy). It can also be used for HR-positive cancer that cannot be treated with surgery, has come back, or has spread.
▸What are common side effects?
The most common side effects are hot flashes, night sweats, and loss of interest in sex. Hormone therapy may also disrupt the menstrual cycle in premenopausal women. Side effects depend on the specific drug you receive.
▸How effective is hormone therapy?
Studies over many decades have shown that hormone therapy, when taken for 5 years or more, can greatly reduce the risk of new breast cancer, breast cancer recurrence, and dying from breast cancer. Your doctor can share how effective it may be for your diagnosis.
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