How do hormone therapies work?

Hormone-positive (ER+) cancers are encouraged to grow by a natural hormone in your body called oestrogen.

Hormone therapies work by stopping oestrogen encouraging tumours to grow. Examples are a type of drug called an aromatase inhibitor or a drug called tamoxifen.

Aromatase inhibitors stop your body from producing oestrogen, while tamoxifen stops the oestrogen in your body from signalling to cancer cells.

If you’re receiving tamoxifen and have not been through the menopause, you may also be offered ovarian suppression. Ovarian suppression uses surgery to remove your ovaries or drugs to stop your ovaries producing oestrogen.

If your cancer is not hormone positive, hormone therapies will probably not help to control it.

Which hormone therapy is right for me?

Hormone therapy is suitable for about seven out of 10 women with ER+ secondary breast cancer. If it’s not suitable for you, your oncologist will recommend other treatment options.

The hormone therapy that is right for you will depend on whether or not you’ve been through the menopause (if you’re female) and which treatments you have received before.

Sometimes, it is hard for doctors to tell whether or not you have been through the menopause, as some cancer treatments stop you having periods. If they are unsure, they can measure levels of hormones in your body to check.

Click on the statement that is applicable to you to learn more:

Hormone therapies for post-menopausal women

If you’ve been through the menopause, you’re likely to be offered an aromatase inhibitor before. The different aromatase inhibitors available are anastrozole, exemestane (Aromasin) and letrozole. If you’ve already received an aromatase inhibitor (to treat your primary breast cancer), your oncologist may recommend that you try a different type of aromatase inhibitor, tamoxifen or a different type of treatment altogether, such as chemotherapy.

  • If in the future your cancer begins to grow despite your treatment, your oncologist will recommend trying a different treatment. One option for some women is taking everolimus (Afinitor) alongside another hormone therapy. Another option is a drug called fulvestrant (Faslodex), although this is not available on the NHS as standard. For information, see our page on Access to Anticancer Drugs.
  • If in the future your cancer begins to grow despite your treatment, your oncologist will recommend trying a different treatment such as everolimus (Afinitor) alongside another hormone therapy or fulvestrant (Faslodex). These drugs are not available on the NHS as standard. For information, see our page on Access to Anticancer Drugs.
  • If in the future your cancer begins to grow despite your treatment, your oncologist will recommend trying a different treatment such as everolimus (Afinitor) alongside another hormone therapy or fulvestrant (Faslodex). Fulvestrant is not available on the NHS as standard. For information, see our page on Access to Anticancer Drugs.
  • If in the future your cancer begins to grow despite your treatment, your oncologist will recommend trying a different treatment such as everolimus (Afinitor) alongside another hormone therapy or fulvestrant (Faslodex). These drugs are not available on the NHS as standard. For information, see our page on Access to Anticancer Drugs.
  • You might also be invited to take part in a clinical trial.

Hormone therapies for pre-menopausal women

If you haven’t been through the menopause (or are partway through the menopause), you’ll probably be offered tamoxifen. You might also be offered ovarian suppression.

If you’ve received tamoxifen before, you may be offered ovarian suppression followed by an aromatase inhibitor. The different aromatase inhibitors available are anastrozole, exemestane (Aromasin) and letrozole. If in the future, your cancer begins to grow despite your treatment, your oncologist will recommend trying a different treatment, such as chemotherapy or a hormone therapy called fulvestrant (Faslodex).

Fulvestrant is only used in women who have been through the menopause. If you have not been through the menopause, you’ll need to have ovarian suppression first. Fulvestrant is not available as standard on the NHS. See our section on Access to anticancer drugs for more information.

You might also be invited to take part in a clinical trial.

Hormone therapies for men

Men with hormone-positive secondary breast cancer are usually offered tamoxifen as their first treatment. If tamoxifen isn’t suitable for you, you’ll be offered a different treatment, such as chemotherapy or an aromatase inhibitor. 

The different aromatase inhibitors available are anastrozole, exemestane (Aromasin) and letrozole. In men they are usually given along with a medication called a luteinising-hormone releasing hormone (LHRH) analogue, such as goserelin (Zoladex).

LHRH analogues reduce the amount of natural oestrogen in your body. If in the future your cancer begins to grow despite your treatment, your oncologist will recommend trying a different treatment.

You might also be invited to take part in a clinical trial.

Are there any serious risks with hormone therapy?

Tamoxifen slightly increases your risk of having a blood clot in a vein (venous thromboembolism).

This risk is higher if you are:

  • Obese
  • Older
  • Having surgery

If you’re at particular risk of having a blood clot, your doctor can prescribe a medicine (an anticoagulant) to reduce this risk.

There is an increased risk of cancer of the lining of the womb (endometrial cancer) if you use tamoxifen for many years, but this is rare.

Aromatase inhibitors can cause weak bones if used for many years, which could put you at risk of fracturing a bone and osteoporosis. You might be offered a scan of your bones before you start treatment.

This is to see whether it might be helpful to give you a bone-strengthening treatment to reduce your risk of having a fracture. A bisphosphonate or a drug called denosumab can strengthen your bones.

Make sure your oncologist explains the risks of the hormone therapy recommended for you, so you’re informed and can balance this up against the possible benefits.

What are the other main side effects of hormone therapy?

All hormone therapies have some side effects and they differ slightly between drugs.

Side effects include:

  • Symptoms similar to the menopause, such as hot flushes, vaginal discharge or dryness, vaginal bleeding, an itchy vulva, mood swings/feeling low, and decreased sex drive
  • Bone pain, joint pain and leg cramps
  • Headaches, eye problems, and rashes
  • Thinner hair
  • Nausea
  • Feeling weak or fatigued and difficulty sleeping

What help is available for side effects?

Treatments can relieve some of your side effects. Hormone replacement therapy (HRT) is not recommended for women with breast cancer. However, other drugs can help relieve menopausal symptoms, such as some antidepressants called selective serotonin reuptake inhibitors (SSRIs).

There are other therapies and lifestyle changes may help with hot flushes, such as acupuncture, exercising and avoiding triggers (e.g. caffeine and alcohol). There is no proof that natural remedies or particular diets help with menopausal symptoms.

If you’d like to try them, speak to your oncologist first, as they could interfere with your hormone therapy and stop it working properly.

Find out more

You can find out more about treatments to help with fatigue and pain in our section on quality of life.

Tips and advice

Advice on getting the best care

To help you feel confident you’re getting the best care, you may want to:

  • Ask your oncologist to explain what your treatment options are, and why they are recommending a particular drug for you
  • Ask whether there are any additional options for you, including new drugs, clinical trials and treatment at other centres
  • Go over the risks and benefits of each treatment with your oncologist
  • Speak up if your treatment is giving you side effects – your treatment team can often help

Information Standard

Information last reviewed: October 2015

Breast Cancer Now's health information is covered by NHS England's Information Standard quality mark. Find out how this resource was developed.