Hormone therapy for metastatic breast cancer

An Asian middle-aged woman looking at a bottle of pills

Hormone therapies are often used as the first treatment for metastatic breast cancer. Hormone therapies only work for breast cancers that are hormone-receptor positive. The benefits of hormone therapy can sometimes last for several years. Hormone therapy can be used alone or together with other drugs. 

How does hormone therapy work? 

Some breast cancers are oestrogen receptor (ER) and progesterone receptor (PR) positive. This means they are encouraged to grow by the female hormone oestrogen. All hormone therapies try to stop oestrogen from helping ER positive breast cancer and PR-positive breast cancer to grow.

If you had a hormone therapy to treat your primary breast cancer, you may need a different type to treat the metastatic cancer. 

The benefits of hormone therapy can sometimes last for several years.


Types of hormone therapy

Different types of hormone therapies work in different ways.

Anti-oestrogen drugs

Anti-oestrogen drugs stop the hormone oestrogen from helping oestrogen-receptor positive cancer cells to grow. They do this by stopping oestrogen from attaching to the receptors on the cancer cells. 

  • What drugs are used?
    Examples of anti-oestrogen drugs are tamoxifen and fulvestrant. Tamoxifen can be given before or after the menopause. Fulvestrant is usually given to women who have been through the menopause.
  • How are they given?
    They are usually given in tablet form. Some may be given as a liquid to be taken by mouth or as an injection.

Aromatase inhibitors

  • How do they work?
    Aromatase inhibitors block the enzyme aromatase, which changes hormones called androgens into oestrogen.
  • What drugs are used?
    Examples of aromatase inhibitors include anastrozole, letrozole and exemestane. 
  • How are they given?
    They are usually given in tablet form.
  • What are the side-effects? 
    Aromatase inhibitors can cause side-effects. They can cause vaginal dryness, nausea, and muscle and joint pain. You may have bone density scans before and during treatment as the drugs can increase bone loss. Treatments that can improve your bone strength are also available.

Ovarian treatments

Ovarian treatments stop your ovaries making oestrogen. They can be temporary (ovarian suppression) or permanent (ovarian ablation). Ovarian treatments may be recommended for women with oestrogen-receptor positive cancer who have not been through the menopause. Ovarian treatments are usually given in combination with an aromatase inhibitor or an anti-oestrogen drug.

  • Drug treatments (usually temporary)
    Drugs are used to ‘switch off’ your ovaries temporarily. The drugs change the levels of the hormones released in your brain that control how your ovaries work. An example of this type of drug is goserelin. When you stop taking the drug, your ovaries should start producing oestrogen again and your periods should return. If you are close to menopausal age, your periods may not return.
  • Surgery (permanent)
    Surgery involves removing your ovaries. Your periods will stop immediately if your ovaries are removed. The operation to remove your ovaries is called an oophorectomy. It may be done using keyhole surgery, usually under general anaesthetic. You may need to stay in hospital for a day or two.
  • Radiotherapy (permanent)
    Radiotherapy uses X-rays to stop your ovaries from working to produce oestrogen. Normally you have one more period, which may be heavy, and then your periods stop completely.

How does the menopause affect the choice of hormone therapy?

If you haven’t been through the menopause, all types of hormone therapies are suitable for you. You may be given a combination of treatments, usually:

  • An ovarian treatment to stop your ovaries from producing oestrogen
  • An anti-oestrogen drug or an aromatase inhibitor to stop oestrogen from helping breast cancer cells to grow

After the menopause the ovaries stop producing oestrogen, so ovarian treatments are not helpful for you. You will most likely be treated with either:

  • An aromatase inhibitor or
  • An anti-oestrogen drug

What are the side-effects of hormone therapy?

Hormone therapy may cause short- or long-term side-effects. As with all treatments, side-effects can vary. Talk to your doctor if you’re troubled by any side-effects. Side-effects include:

Changes to periods and menopausal symptoms

If you are still having menstrual periods, they may become lighter, irregular or stop altogether while you are on treatment. Your periods may come back after treatment, but if you’re close to the age where you would be going through your natural menopause, it’s less likely that your periods will come back.

If your periods stop you may have menopausal symptoms like hot flushes, night sweats, anxiety, lower sex drive (libido), dry skin, vaginal dryness and mood changes. Read more about managing menopausal symptoms. 

Bone loss and pain

Some hormone therapy drugs may increase bone loss and cause pains and aches in your muscle or bone joints.

You may have bone density (DEXA) scans before starting treatment and regularly while on hormone therapy. Drugs may be prescribed if there is serious bone loss (osteopenia). Read more about bone pain and weakened bones

There are also things you can do yourself to improve your bone health such as not smoking, eating calcium-rich foods and taking exercise. Read more about cancer and bone health.

Blood clotting

Some drugs slightly increase the risk of blood clotting. Tell your doctor if you have any chest pain, swelling, or tenderness in your legs or arms or any new shortness of breath.

Thickened womb

Some drugs can cause the lining of your womb to become thickened or put you at a small risk of developing cancer of the womb. For this
reason, you should report any vaginal bleeding to your doctor.

Other hormone therapy side-effects

There are other possible side-effects from hormone therapy drugs. Ask your medical team about your own particular drug treatment – what side-effects to expect and how to manage them. Always contact your doctor if you’re worried. We have more information on side-effects and tips on how to manage them.


Some hormone therapies can cause a permanent menopause. It is not easy to come to terms with infertility, especially as you are already coping with metastatic breast cancer. It can help to share your concerns with someone who is a good listener or with a professional counsellor. We fund free counselling at many local cancer support centres. You can also call our Support Line on 1800 200 700 or visit a Daffodil Centre for information and support from a cancer nurse.

For more information

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