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Hormone therapy for breast cancer

Hormonal therapy - breast cancer; Hormone treatment - breast cancer; Endocrine therapy; Hormone-sensitive cancers - therapy; ER positive - therapy; Aromatase inhibitors - breast cancer

Hormone therapy to treat breast cancer uses drugs or treatments to lower levels or block the action of female sex hormones (estrogen and progesterone) in a woman's body. This helps slow the growth of many breast cancers.

Hormone therapy makes cancer less likely to return after breast cancer surgery. It also slows the growth of breast cancer that has spread to other parts of the body.

Hormone therapy can also be used to help prevent cancer in women at high risk for breast cancer.

It is different from hormone therapy to treat menopause symptoms.

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Hormones and Breast Cancer

The hormones estrogen and progesterone make some breast cancers grow. They are called hormone-sensitive breast cancers. Most breast cancers are sensitive to hormones.

Estrogen and progesterone are produced in the ovaries and other tissues such as fat and skin. After menopause, the ovaries stop producing these hormones. But the body continues to make a small amount.

Hormone therapy only works on hormone-sensitive cancers. To see if hormone therapy may work, doctors test a sample of the tumor that has been removed during surgery to see if the cancer might be sensitive to hormones.

Hormone therapy can work in two ways:

Drugs That Block Estrogen

Some drugs work by blocking estrogen from causing cancer cells to grow.

Tamoxifen (Nolvadex) is a drug that prevents estrogen from telling cancer cells to grow. It has a number of benefits:

Other drugs that work in a similar way are used to treat advanced cancer that has spread:

Drugs That Lower Estrogen Levels

Some drugs, called aromatase inhibitors (AIs), stop the body from making estrogen in tissues such as fat and skin. But, these drugs do not work to make the ovaries stop making estrogen. For this reason, they are used mainly to lower estrogen levels in women who have been through menopause (postmenopausal). Their ovaries no longer make estrogen.

Premenopausal women can take AIs if they are also taking drugs that stop their ovaries from making estrogen.

Aromatase inhibitors include:

Lowering Estrogen Levels From the Ovaries

This type of treatment only works in premenopausal women who have functioning ovaries. It can help some types of hormone therapy work better. It is also used to treat cancer that has spread.

There are three ways to lower estrogen levels from the ovaries:

Any of these methods will put a woman into menopause. This causes symptoms of menopause:

Drug Side Effects

The side effects of hormone therapy depend on the drug. Common side effects include hot flashes, night sweats, and vaginal dryness.

Some drugs can cause less common but more serious side effects, such as:

Weighing the Options

Deciding on hormonal therapy for breast cancer can be a complex and even difficult decision. The type of therapy you receive may depend on whether you have gone through menopause before treatment for breast cancer. It also may depend on whether you want to have children. Talking with your health care provider about your options and the benefits and risks for each treatment can help you make the best decision for you.


American Cancer Society website. Hormone therapy for breast cancer. Updated September 18, 2019. Accessed December 6, 2021.

Henry NL, Shah PD, Haider I, Freer PE, Jagsi R, Sabel MS. Cancer of the breast. In: Niederhuber JE, Armitage JO, Kastan MB, Doroshow JH, Tepper JE, eds. Abeloff's Clinical Oncology. 6th ed. Philadelphia, PA: Elsevier; 2020:chap 88.

National Cancer Institute website. Hormone therapy for breast cancer. Updated July 7, 2021. Accessed December 6, 2021.

Rugo HS, Rumble RB, Macrae E, et al. Endocrine therapy for hormone receptor-positive metastatic breast cancer: American Society of Clinical Oncology Guideline. J Clin Oncol. 2016;34(25):3069-3103. PMID: 27217461


Review Date: 10/28/2021  

Reviewed By: Todd Gersten, MD, Hematology/Oncology, Florida Cancer Specialists & Research Institute, Wellington, FL. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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