• Developed and funded by Pfizer Ltd
What is metastatic breast cancer? ​​​​​​​ How do doctors make treatment decisions?SurgeryRadiotherapyChemotherapyHormone TherapyTargeted Therapy What matters most to you? Your doctor discussion guideYour questions answered
  • AAA+
SurgeryRadiotherapyChemotherapyHormone TherapyTargeted Therapy

​​​​​​​Hormones are chemicals produced naturally in one part of the body to help regulate the activity of cells in other areas of the body. When a hormone is released in the body, it travels through the bloodstream and then binds to proteins called receptors on the surface of the target cells, resulting in a change within that cell.Each hormone produced in our bodies has a specific purpose. For example, the hormone insulin helps to control the level of glucose in our bodies.

​​​​​​​In normal circumstances, these hormones and their effects are well controlled. In cancer, hormonal regulation and effects may be lost, so cells can begin to act in different ways.

How do hormone therapies work?

Hormone therapies  ​​​​​​​work in different ways. These include blocking hormone production in the body or by binding to hormone receptors. This prevents the hormones from acting on cancer cells and can stop their effects.

In breast cancer, hormone therapies target the hormones oestrogen and progesterone  

How do oestrogen and progesterone impact breast cancer?

In women, the hormones oestrogen  and progesterone  are produced naturally by the ovaries and help to regulate the menstrual cycle. After the menopause, oestrogen can be produced from body fat.

In breast cancer, certain types of tumour ​​​​​​​ cells depend on these hormones to grow. This is because they have a lot of oestrogen receptors (ER+) or progesterone receptors (PR+) on them.

It’s important to know the hormone receptor status of your breast cancer (also referred to as the tumour biology). If your breast cancer expresses hormone receptors, specific treatments help to restrict exposure of the tumour to these hormones which should help to prevent its growth.

Why is hormone therapy given for metastatic breast cancer?

Hormone therapies  work in a variety of ways to disrupt oestrogen  production and block its effects.

If you’ve had breast cancer before, your doctor will ask if you received previous hormone therapy. This may affect the type of hormone therapy you receive for metastatic breast cancer .

Types of hormone therapy for HR+ breast cancer

There are many different types of hormone therapy  used in the treatment of metastatic breast cancer , these include:

Type of treatment Action
Aromatase Inhibitors

Block the function of the ovaries to reduce oestrogen levels                                                  
Ovarian Ablation (Surgery to remove ovaries, radiation treatment)

Block the function of the ovaries to reduce oestrogen levels
Selective Oestrogen  Receptor Modulator (SERMs)
Block the effects of oestrogen by preventing it binding to cell receptors
Selective Oestrogen Receptor Down-Regulator (SERDs)
Block the effects of oestrogen by reducing the number of receptors

If you are pre-menopausal, you may also receive a treatment called a luteinising hormone-releasing hormone (LHRH) agonist ​​​​​​​ alongside hormone therapy. This temporarily suppresses oestrogen production from your ovaries.

What if your breast 
​​​​​​​cancer is not hormone receptor-positive?

Hormone therapy  will not be appropriate but there are other treatment options available for people who do not test positive for hormone receptors.

There are targeted therapies for HER2 + breast cancer

Learn more about HER2+ targeted therapy

learn more about her2+ targeted therapyLoading

If your cancer is HR-/HER2- (triple negative), there are other options such as chemotherapy  or targeted therapy ​​​​​​​.

Learn more about HR-/HER2- targeted therapy

learn more about the her/her2- targeted therapyLoading

Learn more about chemotherapy

leran more about chemotherapyLoading

How is hormone therapy given?

Most hormone therapies  such as aromatase inhibitors and SERMs can be taken orally as a tablet or capsule. These treatments are given continuously (e.g. you will take a tablet every day). Your doctor will discuss with you how your treatment should be taken and the length of time you may be on the treatment for.

A few therapies such as SERDs are given as an injection into the muscle.These treatments are given in cycles. The number of cycles you receive, and the length of time in between cycles might vary. Your doctor will discuss this with you.
Hormone therapies can be given alone or in combination with a targeted therapy. ​​​​​​​ Your doctor will discuss what combination of treatments might be suitable for you.

What are the side effects of hormone therapy?

Hormone therapies can cause side effects. These will vary from person to person and will depend on the specific hormone treatment. Talk to your doctor about the potential side effects of hormone therapy  and the treatments that may be the best option for you.

Click here to learn more about the side effects of hormone therapyLoading

How does hormone therapy affect the menopause?

Hormone therapies reduce the level of oestrogen ​​​​​​​ in the body. When hormone therapy is given to a pre- or peri- menopausal woman, it is often combined with a treatment that temporarily suppresses the ovaries (such as an LHRH agonist ​​​​​​​). This also reduces oestrogen levels.

The reduction in oestrogen can cause the onset of the menopause and menopausal symptoms. With certain treatments, this can be temporary.

click here to learn more about hormone therapy and menopauseLoading



The What’s Breast for Me? Campaign is funded by Pfizer Healthcare Ireland. Copyright © 2024 Pfizer Healthcare Ireland. All rights reserved. This site is intended for residents of the Republic of Ireland. The information provided on this site is intended for general information and education and is not intended to be a substitute for advice provided by a doctor or other qualified healthcare professional. All decisions regarding patient care must be made with a healthcare provider, considering the unique characteristics of the patients.


Date of preparation: January 2024