Hormone Therapy for Breast Cancer: Types, How It Works, and Side Effects
Updated: 6 days ago
Written and medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026 · How we review
Quick Answer: What is hormone therapy for breast cancer?
Hormone therapy for breast cancer is a treatment for hormone receptor-positive (HR+) breast cancer that lowers estrogen levels or blocks hormones from reaching cancer cells. It is usually a daily pill or regular injection, often given after surgery to lower the risk of the cancer coming back, and most people take it for at least five years. [1]
What the research says
Five years of tamoxifen cuts recurrence by nearly half in early ER+ breast cancer. A patient-level meta-analysis of 20 trials (21,457 women; 10,645 with ER+ disease) found tamoxifen lowered recurrence during years 0–4 (rate ratio 0.53) and reduced breast cancer deaths by about a third over 15 years. (EBCTCG, Lancet, 2011) [2]
Aromatase inhibitors outperform tamoxifen after menopause. In 31,920 postmenopausal women with ER+ early breast cancer, 5 years of an aromatase inhibitor lowered 10-year breast cancer mortality versus 5 years of tamoxifen (12.1% vs 14.2%), with fewer endometrial cancers (0.4% vs 1.2%) but more fractures (5-year risk 8.2% vs 5.5%). (EBCTCG, Lancet, 2015) [3]
Ten years of tamoxifen beats five. In the ATLAS trial (6,846 women with ER+ disease), continuing tamoxifen to 10 years lowered breast cancer mortality in years 5–14 from 15.0% to 12.2% and recurrence from 25.1% to 21.4%. (Davies et al., Lancet, 2013) [4]
Key takeaways
Hormone therapy (also called endocrine therapy) treats breast cancers that use estrogen or progesterone to grow. [1]
About 3 in 4 breast cancers are hormone receptor-positive. [1]
It works by lowering the body's estrogen or by blocking or destroying the receptors on cancer cells. [1]
The best drug depends largely on whether you have gone through menopause. [1]
Most people take it for at least five years after surgery. [1]
Side effects such as hot flashes and joint pain are common but often manageable. [1]
Who needs hormone therapy for breast cancer?
Hormone therapy for breast cancer is for people whose tumor is hormone receptor-positive (HR+), meaning the cancer cells rely on estrogen, progesterone or both to grow. [1]
Your body makes these hormones naturally. A pathology report labels an HR+ tumor as:
ER+: estrogen receptor-positive
PR+: progesterone receptor-positive
Both ER+ and PR+
ER+ breast cancer is the most common type of breast cancer, and HR+ cancers make up about 3 out of every 4 cases. [1] If you want to understand what your report means, see our guide to hormone receptor-positive (HR+) breast cancer.
Hormone therapy helps both women and men. It is a standard part of treatment for male breast cancer as well. [1]
How does hormone therapy for breast cancer work?
Hormone therapy for breast cancer works by starving HR+ cancer cells of the hormones they need to grow. [1]
It does this in one of two ways:
Lowering the estrogen your body makes. Some drugs reduce how much estrogen is produced.
Blocking or removing the receptor. Other drugs stop estrogen from attaching to cancer cells, or destroy the receptors entirely. [1]
When do doctors use hormone therapy for breast cancer?
Doctors use hormone therapy for breast cancer before surgery, after surgery, for advanced cancer, and sometimes to lower cancer risk in high-risk people. [1]
When it's used | Main goal |
After surgery (adjuvant) | Lower the risk of the tumor growing back |
Before surgery (neoadjuvant) | Shrink the tumor so it is easier to remove |
Advanced or incurable cancer | Help some people live longer |
Prevention | Lower the chance of some HR+ cancers in people with a high lifetime risk |
It is often combined with breast cancer surgery. [1]
What are the types of hormone therapy for breast cancer?
The five main types of hormone therapy for breast cancer are aromatase inhibitors, ovarian function suppression, SERMs, SERDs and PROTACs. [1]
Drug class | How it works | Common examples | Typically used for |
Aromatase inhibitors | Lower the amount of estrogen the body makes | Anastrozole, exemestane, letrozole | ER+ cancer after menopause |
Ovarian function suppression | Stop the ovaries from making estrogen | Goserelin, leuprolide | ER+ cancer before menopause |
Selective estrogen receptor modulators (SERMs) | Block estrogen at the cancer cell | Tamoxifen (raloxifene is used only to lower risk) | ER+ breast cancer |
Selective estrogen receptor down regulators (SERDs) | Keep estrogen from connecting to cancer cells | Fulvestrant, elacestrant, imlunestrant, camizestrant | ER+ breast cancer |
Proteolysis targeting chimeras (PROTACs) | Trigger destruction of multiple estrogen receptors in a continuous loop | Vepdegestrant | A newer treatment option |
PROTACs are the newest class. Instead of only blocking receptors, they keep destroying them. [1]
How does menopause change hormone therapy for breast cancer?
Menopause changes hormone therapy for breast cancer because it changes where your body makes estrogen. [1]
Before menopause, the ovaries make most estrogen.
After menopause, estrogen comes from tissue such as fat and muscle. [1]
Before menopause | After menopause | |
Main source of estrogen | Ovaries | Fat, muscle and other tissue |
Most common treatment | Tamoxifen, or ovarian function suppression plus an aromatase inhibitor | An aromatase inhibitor, or an aromatase inhibitor followed by tamoxifen |
If you were diagnosed before menopause, our guide to breast cancer in young women covers more of what to expect.
What happens during hormone therapy for breast cancer?
Hormone therapy for breast cancer is usually a pill you take once a day, though some types are given as regular injections at your provider's office. [1]
Depending on your cancer, your plan may also include:
Chemotherapy: kills cancer cells throughout the body
Targeted therapy: blocks proteins that help cancer grow [1]
Your care team should explain why each part of your plan fits your situation.
How long does hormone therapy for breast cancer last?
Hormone therapy for breast cancer usually lasts at least five years after surgery. [1]
You may need it longer if your risk of the cancer coming back is high. Even at lower risk, staying on treatment beyond five years may still offer benefits, so ask your oncologist what they recommend. [1] Long-term trial data support this: continuing tamoxifen to 10 years lowered both recurrence and breast cancer deaths compared with stopping at five. [4]
How effective is hormone therapy for breast cancer?
Hormone therapy for breast cancer is highly effective for HR+ disease. [1]
Large trial overviews in the early 1990s showed that women treated with tamoxifen lived longer than those who were not, which helped make hormone therapy the standard of care. [1][5] Today, it is known to:
Help both men and women with breast cancer live longer
Lower the chance of the cancer coming back
Lower the risk of a new breast cancer forming [1]
Taking hormone therapy for five years or more can greatly reduce the risk of a new breast cancer. [7]
What are the side effects of hormone therapy for breast cancer?
The most common side effects of hormone therapy for breast cancer are hot flashes, fatigue, and joint and muscle pain, but they vary by person and by drug type. [1]
Area affected | Possible side effects |
Body temperature | Hot flashes, night sweats |
Energy and digestion | Fatigue, nausea |
Muscles and joints | Pain or stiffness |
Periods and sexual health | Changes in periods, loss of interest in sex, vaginal dryness |
Mood | Mood swings |
Bones | Weaker bones and a higher risk of osteoporosis |
For most people, the life-saving benefits outweigh these effects. [1] Tell your provider early if side effects bother you. Options include diet changes for nausea and fatigue, medicines that ease symptoms, or switching to a different drug type. [1] For practical relief tips, see our guide to hot flashes.
When should you call a doctor during hormone therapy for breast cancer?
You should call your doctor during hormone therapy for breast cancer if you develop new side effects or signs that the cancer may have come back. [1]
Contact your care team promptly if you notice:
A new lump in your breast
Pain in your chest, belly or bones
Trouble breathing
A headache that will not go away [1]
Seek emergency care right away if you have severe trouble breathing or chest pain. If you take tamoxifen, also get care quickly for leg pain or swelling, sudden weakness or trouble speaking, or any unusual vaginal bleeding, because it can rarely cause blood clots, stroke or uterine cancer.
Is hormone therapy better than chemotherapy for breast cancer?
Hormone therapy is recommended for most people with HR+ breast cancer, but whether it is "better" than chemotherapy depends on your diagnosis. [1]
Hormone therapy | Chemotherapy | |
Targets | Only cancer cells with hormone receptors | Cancer cells throughout the body, with or without receptors |
How it works | Starves cancer cells of the hormones they need to grow | Destroys cancer cells throughout the body |
When it's recommended | Most people with HR+ breast cancer | Depends on your diagnosis |
Many people receive both. Learn more about chemotherapy drugs and their side effects.
Is hormone therapy for breast cancer the same as hormone therapy for menopause?
Hormone therapy for breast cancer is not the same as hormone therapy for menopause; they work in opposite directions. [1]
Menopause hormone therapy adds hormones to relieve symptoms.
Breast cancer hormone therapy blocks cancer cells from using the hormones already in your body. [1]
What should you eat during hormone therapy for breast cancer?
During hormone therapy for breast cancer, the best approach is a balanced eating pattern built on fruits, vegetables, whole grains and lean protein. [1]
Try to limit processed foods high in sugar or fat. [1] Some research links moderate amounts of foods rich in phytoestrogens, such as soy and green tea, with a lower risk of recurrence in ER+ breast cancer. [1][6] Still, overall eating habits matter more than any single food, so ask your provider what a healthy meal plan looks like for you. [1]
What if you don't want hormone therapy for breast cancer?
If you don't want hormone therapy for breast cancer, talk openly with your oncologist about your concerns and other options. [1]
Treatment plans are based on your cancer type, overall health and personal preferences. Take time to weigh the risks and benefits before deciding. [1] Our overview of breast cancer symptoms, causes and treatment can help you understand the full range of options.
Conclusion
Hormone therapy is one of the most effective tools against HR+ breast cancer. It lowers estrogen or blocks it from reaching cancer cells, and it reduces the chance of the cancer returning. The right drug depends mostly on your menopause status, and treatment usually lasts five years or more. Side effects are real, but your care team can help you manage them.
Your next step: Write down your questions about drug type, treatment length and side effects, and bring them to your next oncology visit. Then explore our breast cancer guides to keep learning with clear, evidence-based information you can trust.
FAQ
What is hormone therapy for breast cancer?
Hormone therapy for breast cancer is a treatment that lowers estrogen or blocks hormones from reaching cancer cells in hormone receptor-positive (HR+) breast cancer. It is also called endocrine therapy and is usually taken as a daily pill or regular injection.
Who should get hormone therapy for breast cancer?
Hormone therapy for breast cancer is recommended for people whose tumor is estrogen receptor-positive (ER+), progesterone receptor-positive (PR+) or both.
How long do you take hormone therapy for breast cancer?
Hormone therapy for breast cancer is usually taken for at least five years after surgery. Your oncologist may recommend a longer course if your risk of recurrence is high.
What are the most common side effects of hormone therapy for breast cancer?
The most common side effects of hormone therapy for breast cancer include hot flashes, night sweats, fatigue, and joint and muscle pain. Some drugs can also weaken bones, cause vaginal dryness or change your periods.
Is tamoxifen or an aromatase inhibitor better for breast cancer?
Tamoxifen and aromatase inhibitors each suit different people, mainly based on menopause status. After menopause, an aromatase inhibitor is the most common choice; before menopause, tamoxifen or ovarian function suppression with an aromatase inhibitor is more common.
Is hormone therapy for breast cancer the same as HRT for menopause?
Hormone therapy for breast cancer is not the same as menopause hormone therapy (HRT). HRT adds hormones to ease symptoms, while breast cancer hormone therapy blocks cancer cells from using hormones.
Can men take hormone therapy for breast cancer?
Men with HR+ breast cancer can take hormone therapy, and it helps them live longer, just as it does for women.
When should I call my doctor during hormone therapy?
Call your doctor during hormone therapy if you notice a new breast lump, pain in your chest, belly or bones, trouble breathing, or a headache that won't go away. These can be signs the cancer has returned.
Can hormone therapy for breast cancer weaken my bones?
Some hormone therapies, especially aromatase inhibitors, can cause bone loss. Your doctor may check your bone density and suggest calcium, vitamin D, exercise or medicine to protect your bones.
What is ovarian suppression?
Ovarian suppression stops the ovaries from making estrogen, using medicine or, less often, surgery. It is sometimes used with other hormone therapy in people who have not gone through menopause.
Related Reading
Chemotherapy for Breast Cancer: Types, Timing and Side Effects explains chemotherapy for breast cancer.
References
Cleveland Clinic. Hormone Therapy for Breast Cancer. Cleveland Clinic. Last updated September 28, 2026. https://my.clevelandclinic.org/health/treatments/hormone-therapy-for-breast-cancer
Early Breast Cancer Trialists' Collaborative Group (EBCTCG); Davies C, Godwin J, Gray R, et al. Relevance of breast cancer hormone receptors and other factors to the efficacy of adjuvant tamoxifen: patient-level meta-analysis of randomised trials. Lancet. 2011;378(9793):771-784. PMID 21802721. https://doi.org/10.1016/S0140-6736(11)60993-8
Early Breast Cancer Trialists' Collaborative Group (EBCTCG). Aromatase inhibitors versus tamoxifen in early breast cancer: patient-level meta-analysis of the randomised trials. Lancet. 2015;386(10001):1341-1352. PMID 26211827. https://doi.org/10.1016/S0140-6736(15)61074-1
Davies C, Pan H, Godwin J, et al. Long-term effects of continuing adjuvant tamoxifen to 10 years versus stopping at 5 years after diagnosis of oestrogen receptor-positive breast cancer: ATLAS, a randomised trial. Lancet. 2013;381(9869):805-816. PMID 23219286. https://doi.org/10.1016/S0140-6736(12)61963-1
Early Breast Cancer Trialists' Collaborative Group. Systemic treatment of early breast cancer by hormonal, cytotoxic, or immune therapy. 133 randomised trials involving 31,000 recurrences and 24,000 deaths among 75,000 women. Lancet. 1992;339(8784):1-15. PMID 1345950. https://pubmed.ncbi.nlm.nih.gov/1345950/
van Die MD, Bone KM, Visvanathan K, et al. Phytonutrients and outcomes following breast cancer: a systematic review and meta-analysis of observational studies. JNCI Cancer Spectr. 2024;8(1):pkad104. PMID 38070485. https://doi.org/10.1093/jncics/pkad104
National Cancer Institute. Hormone Therapy for Breast Cancer. National Cancer Institute. Last updated September 23, 2026. https://www.cancer.gov/types/breast/treatment/hormone-therapy
National Cancer Institute, Surveillance, Epidemiology, and End Results (SEER) Program. Cancer Stat Facts: Female Breast Cancer Subtypes. SEER. Accessed October 31, 2026. https://seer.cancer.gov/statfacts/html/breast-subtypes.html
Medical disclaimer
This article is for general educational purposes only and is not a substitute for professional medical advice, diagnosis or treatment. Always talk with your oncologist or another qualified healthcare provider about your own situation before starting, stopping or changing any treatment. If you think you may have a medical emergency, call your local emergency number right away.
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