The Who, What, Where, When and Sometimes, Why.

Hormone Therapies

Watch our Breast Cancer Breakthrough series episode 9, “New Frontiers in Early ER-positive Breast Cancer.”

Hormones, hormone receptors and hormone therapy

Estrogen and progesterone are female hormones produced in the body. Some breast cancer cells need estrogen to grow.

When these hormones attach to special proteins called hormone receptors, the cancer cells with these receptors grow.

Hormone therapies slow or stop the growth of hormone receptor-positive tumors by preventing the cancer cells from getting the hormones they need to grow.

Hormone therapies may also be called endocrine therapies. The endocrine system in the body makes hormones.

Hormone receptor status and hormone therapy

All tumors are checked for hormone receptors. A pathologist determines the hormone receptor status by testing the tumor tissue removed during a biopsy.

  • Hormone receptor-positive (estrogen receptor-positive/progesterone receptor-positive) tumors express hormone receptors. This means they have a lot of hormone receptors.
  • Hormone receptor-negative (estrogen receptor-negative/progesterone receptor-negative) tumors do not express hormone receptors. This means they have few or no hormone receptors.

Hormone therapies are only used to treat hormone receptor-positive breast cancers. Most breast cancers are hormone receptor-positive.

Learn more about hormone receptor status.

Estrogen receptor status and progesterone receptor status

Breast cancers that are ER-positive tend to be PR-positive. And cancers that are ER-negative tend to be PR-negative.

Hormone therapy and metastatic breast cancer treatment

Learn more about hormone therapies used to treat metastatic breast cancer.

How do hormone therapies work?

Hormone therapy drugs slow or stop the growth of hormone receptor-positive breast cancers in a few ways:

  • Some hormone therapies, such as tamoxifen, attach to the hormone receptor in the cancer cell and block estrogen from attaching to the receptor.
  • Others, such as aromatase inhibitors and ovarian suppression, lower the level of estrogen in the body so the cancer cells can’t get the estrogen they need to grow.

Benefits of hormone therapies in early and locally advanced breast cancer treatment

For hormone receptor-positive early and locally advanced breast cancers, treatment with the hormone therapies tamoxifen and/or an aromatase inhibitor lowers the risk of [89-91]:

  • Breast cancer recurrence (a return of breast cancer)
  • Breast cancer in the opposite breast
  • Death from breast cancer

Premenopausal women who get ovarian suppression plus tamoxifen or an aromatase inhibitor may lower these risks more than premenopausal women who get tamoxifen alone [92-93].

Learn more about tamoxifen.

Learn more about aromatase inhibitors.

Learn more about ovarian suppression.

Learn about hormone therapies in the treatment of metastatic breast cancer.

Hormone therapy options for early and locally advanced breast cancer

For women with hormone receptor-positive breast cancer, hormone therapy drug options depend on whether or not they have gone through menopause.

Men with hormone receptor-positive breast cancer most often take tamoxifen.

 Hormone therapy options for early and locally advanced breast cancer

Premenopausal (before menopause) women

Postmenopausal (after menopause) women



Tamoxifen plus ovarian suppression

Aromatase inhibitor plus ovarian suppression


Aromatase inhibitor


Aromatase inhibitor plus androgen deprivation therapy

Hormone therapy and CDK4/6 inhibitors

CDK4/6 inhibitors are drugs designed to interrupt the growth of cancer cells. CDK4/6 inhibitors include abemaciclib (Verzenio), palbociclib (Ibrance) and ribociclib (Kisqali).

Early and locally advanced breast cancer

The CDK4/6 inhibitor abemaciclib is used in combination with hormone therapy to treat some hormone receptor-positive early breast cancers at high risk of recurrence.

Learn more about abemaciclib and early breast cancer treatment.

Metastatic breast cancer

The CDK4/6 inhibitors abemaciclib, palbociclib and ribociclib are used in combination with hormone therapy to treat some hormone receptor-positive metastatic breast cancers.

Learn more about CDK4/6 inhibitors and metastatic breast cancer treatment.

Hormone therapy versus menopausal hormone therapy

Hormone therapy for breast cancer treatment is different than menopausal hormone therapy (MHT).

  • Hormone therapies used in breast cancer treatment act as “anti-hormone” or “anti-estrogen” therapies. They block hormone actions or lower hormone levels in the body.
  • MHT is used to increase hormone levels in the body to treat menopausal symptoms.

MHT increases the risk of breast cancer. It’s not usually recommended for women with breast cancer. For other women, it’s only recommended at the lowest dose, for the shortest time needed, to ease menopausal symptoms [94].

MHT is also called postmenopausal hormone use or hormone replacement therapy (HRT).

Learn more about MHT and breast cancer risk.

Learn more about MHT and breast cancer survival.

Learn about other ways to ease menopausal symptoms.

Hormone therapy drugs for early and locally advanced breast cancer

Hormone therapies for early and locally advanced breast cancer


Brand name

Used in pre- or postmenopausal women?

Injection or pill?




Pre- and postmenopausal


Aromatase inhibitors













Ovarian suppression drugs









Learn about hormone therapy drugs for metastatic breast cancer.

To learn more about a specific hormone therapy, visit the National Institutes of Health’s Medline Plus website.    

Click on the topics below to learn more.

Tamoxifen can be used to treat hormone-receptor positive breast cancer in:

  • Premenopausal women
  • Postmenopausal women
  • Men

Premenopausal women may get tamoxifen plus ovarian suppression.

Learn more about tamoxifen.

Learn more about tamoxifen with ovarian suppression.

Aromatase inhibitors can be used to treat hormone-receptor positive breast cancer in:

  • Postmenopausal women
  • Some premenopausal women who also get ovarian suppression

Learn more about aromatase inhibitors.

Learn more about aromatase inhibitors with ovarian suppression.

Ovarian suppression can slow the growth of hormone receptor-positive breast cancer in premenopausal women. It uses drug therapy or surgery to prevent the ovaries from making estrogen. 

Ovarian suppression is always given in combination with tamoxifen or an aromatase inhibitor. It’s never given alone. So, having ovarian suppression doesn’t mean you can avoid taking tamoxifen or an aromatase inhibitor.

Learn more about ovarian suppression.

Different hormone therapies have different side effects.

Before you begin treatment with hormone therapy, talk with your health care provider about possible side effects and how to manage them.

Learn about the side effects of tamoxifen.

Learn about the side effects of aromatase inhibitors.

Learn about the side effects of ovarian suppression.

It’s important to follow the treatment plan (for medications and other therapies) prescribed by your health care provider in terms of:

  • Timing
  • Dose
  • Frequency

Breast cancer treatment is most effective when all parts of the treatment plan are followed as prescribed.

Completing hormone therapy

To get the most benefit from hormone therapy, you need to take the full recommended course of treatment. People who complete the full course have better survival than those who don’t [95-97].

Hormone therapy with tamoxifen and/or an aromatase inhibitor is prescribed for 5-10 years. The length of treatment along with side effects, such as menopausal symptoms, can make it tough to complete treatment. Talk with your health care provider about ways to ease these and other side effects.

If you have trouble remembering to take your medicine, a pillbox or setting an alarm on your watch or phone (you may be able to download an app) may help.

However, you don’t need to worry if you miss a day or two.

Learn more about the importance of following your breast cancer treatment plan.

Learn about ways to manage hot flashes and other menopausal symptoms.

  • What tests were done on my tumor? What were the estrogen receptor status and progesterone receptor status of my tumor? How do these affect my treatment plan?
  • Do I need hormone therapy? Why or why not?
  • Which hormone therapy(s) do you recommend for me and why?
  • Should my tumor be tested with Oncotype DX®, MammaPrint® or other tumor profiling test to help decide if I need chemotherapy?
  • How will hormone therapy affect my risk of a local breast cancer recurrence, metastasis or a new breast cancer? Please explain the differences.
  • In what form and how often will the hormone therapy(s) be given?
  • Is there a generic form of this hormone therapy?
  • How long will I be on hormone therapy? How will that decision be made?
  • How soon after surgery will I begin hormone therapy?
  • What happens if I miss taking a hormone therapy pill once in a while?
  • Should I take the CDK4/6 inhibitor drug abemaciclib (Verzenio) to help lower my risk of breast cancer recurrence?
  • What is the best way for me to treat menopausal symptoms, such as hot flashes? What can I do to manage vaginal dryness and/or painful intercourse?
  • What are the other short-term and long-term side effects of this hormone therapy? What side effects should I report to you?
  • Are there medications I should avoid while using hormone therapy?
  • If I take an aromatase inhibitor, how will my bone density be monitored? What can be done to prevent bone density loss?
  • Is there a clinical trial I can join?
  • Should I see my regular physician or gynecologist during my treatment?
  • How often will I have check-ups and follow-up tests after treatment ends?
  • Will a follow-up care plan be prepared for me?
  • Which health care provider is in charge of my follow-up care?
  • Where can I find information about support groups and other types of support for me and my loved ones?
  • What do I need to consider before treatment if I would like to have a child after being treated for breast cancer?
  • Who will talk with me about the cost of my treatment, including the expenses covered by my insurance and the costs I should expect to pay out-of-pocket?

Learn more about talking with your health care team.

If you’ve been recently diagnosed with breast cancer or feel too overwhelmed to know where to begin to gather information, Susan G. Komen® has a Questions to Ask Your Doctor About Hormone Therapy and Side Effects resource that might help.

You can download and print it to take with you to your next doctor’s appointment or you can save it on your computer, tablet or phone using an app such as Adobe. Plenty of space and a notes section are provided to write or type the answers to the questions.

There are other Questions to Ask Your Doctor resources on many different breast cancer topics you may wish to download.

Treatment guidelines

Although the exact treatment for breast cancer varies from person to person, evidence-based guidelines help make sure high-quality care is given. These guidelines are based on the latest research and agreement among experts.

The National Comprehensive Cancer Network (NCCN) and the American Society of Clinical Oncology (ASCO) are respected organizations that regularly review and update their guidelines.

In addition, the National Cancer Institute (NCI) has treatment overviews.

Talk with your health care team about which treatment guidelines they follow.

After you get a recommended treatment plan from your health care team, study your treatment options. Together with your health care team, make thoughtful, informed decisions that are best for you. Each treatment has risks and benefits to consider along with your own values and lifestyle.

Prescription drug assistance

Hormone therapy drug costs can quickly become a financial burden for you and your family.

Medicare and many insurance companies offer prescription drug plans. One may already be included in your policy, or you may be able to buy an extra plan for prescriptions.

Most hormone therapies are pills, so they’re covered under your health insurance plan’s prescription drug benefit rather than the plan’s medical benefit. This means there are usually out-of-pocket costs, which can add up over time.

You may qualify for programs that help with drug costs or offer low-cost or free prescriptions.

Tamoxifen and aromatase inhibitors (anastrozole, exemestane and letrozole) all have generic forms. Generic drugs cost less than name brand drugs but are just as effective.

Many cancer centers have financial counselors who can discuss insurance and cost coverage with you.

Learn more about insurance plans and prescription drug assistance programs.  

Learn about other financial assistance programs.

Komen Financial Assistance Program

Susan G. Komen® created the Komen Financial Assistance Program to help those struggling with the costs of breast cancer treatment by providing financial assistance to eligible individuals.

To learn more about this program and other helpful resources, call the Komen Breast Care Helpline at 1-877 GO KOMEN (1-877-465-6636) or email

Se habla español.

Susan G. Komen®‘s position on fairness in oral cancer drug coverage

Insurance coverage of oral cancer drugs

Cancer medications given through an IV into a vein or by an injection (under the skin or into a muscle) are usually covered under a health insurance plan’s medical benefit. However, oral cancer drugs (cancer medications that are pills) are usually covered under a health insurance plan’s prescription drug benefit.

As a result, people often find themselves facing high out-of-pocket costs when filling prescriptions for oral cancer drugs. Sometimes these costs can be thousands of dollars a month.

The impact of high cost-sharing

High prescription drug costs and the resulting out-of-pocket burden on patients are a barrier to care. They can prevent people from getting the medications prescribed by their health care providers.

No one should be forced to get less appropriate treatment because an insurer gives more coverage for IV and injectable drugs than for pills.

Efforts to increase fairness in drug coverage

Komen supports state and federal efforts to require insurers to provide the same or better coverage for oral cancer drugs as they do for IV and injectable cancer drugs. This would help make sure patients have access to affordable, appropriate treatment.

Become a Komen Advocacy Insider

Sign up to be a Komen Advocacy Insider and get informed when action is needed on drug coverage issues at the state or national level.


Clinical trials

Research is ongoing to improve all areas of treatment for breast cancer.

New therapies are being studied in clinical trials. The results of these studies will decide whether these therapies become part of the standard of care.

After discussing the benefits and risks with your health care provider, we encourage you to consider joining a clinical trial.

Susan G. Komen® Patient Care Center

If you or a loved one needs information or resources about clinical trials, the Patient Care Center can help. Contact the Komen Breast Care Helpline at 1-877-465-6636 or email

Se habla español. in collaboration with Komen offers a custom matching service to help find clinical trials that fit your needs.

Learn what else Komen is doing to help people find and participate in breast cancer clinical trials, including trials supported by Komen.

Learn more about clinical trials.


Komen Perspective

Read our perspective on clinical trials.*


Susan G. Komen® Support Resources

  • Do you need help? We’re here for you. The Komen Patient Care Center is your trusted, go-to source for timely, accurate breast health and breast cancer information, services and resources. Our navigators offer free, personalized support to patients, caregivers and family members, including education, emotional support, financial assistance, help accessing care and more. Get connected to a Komen navigator by contacting the Breast Care Helpline at 1-877-465-6636 or email to get started. All calls are answered Monday through Thursday, 9 a.m to 7 p.m. ET and Friday, 9 a.m. to 6 p.m. ET. Se habla español.
  • The Komen Breast Cancer and Komen Metastatic (Stage IV) Breast Cancer Facebook groups are places where those with breast cancer and their family and friends can talk with others for friendship and support.
  • Our fact sheets, booklets and other education materials offer additional information.


*Please note, the information provided within Komen Perspectives articles is only current as of the date of posting. Therefore, some information may be out of date. 

Updated 06/25/24



Fact Sheet


Questions to Ask Your Doctor

Hormone Therapy and Side Effects


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