Fulvestrant (Faslodex)

Fulvestrant, also called Faslodex, is a type of hormone treatment. It’s used to treat breast cancer that has spread in women who’ve been through the menopause.

It’s suitable for people whose breast cancer is sensitive to the female hormone oestrogen.

Fulvestrant is the generic (non-branded) name of the drug. Faslodex is its brand name.

Who fulvestrant is for

Fulvestrant is used to treat women who’ve gone through the menopause (post-menopausal).

It’s given to women whose breast cancer has spread to areas around the breast, such as the lymph nodes above or below the collarbone (regional recurrence), or to other parts of the body (secondary breast cancer).

It may also occasionally be prescribed for pre-menopausal women depending on individual circumstances. Your specialist team will discuss with you what they recommend and why.

How it works

The hormone oestrogen can play a part in stimulating some breast cancers to grow. Fulvestrant will only be prescribed if your breast cancer has receptors within the cells that bind to the female hormone oestrogen, known as oestrogen receptor positive or ER+ breast cancer. When oestrogen binds to these receptors, it can stimulate the cancer to grow.

This will usually have been tested using tissue from a biopsy or after surgery for your primary breast cancer. However, if you have secondary breast cancer your specialist may discuss taking a sample of tissue from the secondary breast cancer site to retest the hormone receptors. This will depend on your individual situation.

Fulvestrant works by blocking the action of oestrogen on the cancer cells. It binds to the oestrogen receptors, making them change shape and stop working. It also reduces the number of oestrogen receptors in the breast cancer cells. This is called down-regulation.

If your cancer is oestrogen receptor negative, then fulvestrant will not be of any benefit to you.

When it’s prescribed

Fulvestrant may be prescribed if your breast cancer has progressed while you’re taking, or after you’ve had, other hormone treatments. It can still be effective after other hormone therapies have stopped working because it works in a different way.

You may also be offered fulvestrant as part of a clinical trial.

How fulvestrant is given

Fulvestrant is given by two injections, one in each buttock. These are known as intramuscular (IM) injections.

It’s usually given every two weeks for the first three doses, then once a month. It may be given either at the hospital or at your local doctor’s surgery.

How long it’s given for

You’ll usually be given fulvestrant for as long as it keeps your breast cancer under control. This will vary from person to person and your specialist team will talk to you about your individual situation.

Other drugs

Don’t take drugs containing oestrogen, such as hormone replacement therapy (HRT), while you’re having fulvestrant.

As fulvestrant is given by injection, you need to tell your specialist if you’re taking any anti-coagulants (blood-thinning drugs).

Side effects

Most people having fulvestrant have mild side effects. However, everyone reacts differently to drugs and some people experience more side effects than others.

You may have some or none of the side effects listed below.

If you have persistent side effects from fulvestrant, tell your specialist team so they can decide how best to manage them.

Common side effects

Common side effects of fulvestrant include:

  • menopausal symptoms, such as hot flushes or night sweats
  • nausea (feeling sick).

To find out more about coping with these side effects see our information on menopausal symptoms and sex and intimacy.

Less common side effects

Other possible side effects include:

  • vomiting
  • loss of appetite
  • diarrhoea
  • general weakness or lack of energy
  • urine infections
  • constipation
  • skin rashes
  • headaches
  • bone or joint pain.

A small number of people have temporary pain and inflammation around the injection site.

Fulvestrant also increases the risk of deep vein thrombosis or DVT (a blood clot in a deep vein, usually in the leg). Tell your doctor straight away if you have a swelling or pain in your leg. People with DVT are at risk of developing a pulmonary embolism. This is when part of the blood clot breaks away and travels to the lung.

If you experience shortness of breath, chest pain or cough up blood, see a doctor urgently.

Fulvestrant can cause changes in your liver. This doesn’t usually cause any symptoms but your specialist team will ask you to have regular blood tests to check if your liver is working properly.

Rare side effects

Rare side effects include vaginal discharge or vaginal bleeding, which may occur in the first few weeks of treatment, usually after changing from another hormone therapy to fulvestrant.

If you have vaginal bleeding at any time, tell your doctor or breast care nurse.

Fulvestrant can reduce the number of platelets, which help the blood to clot. This may mean you bruise or bleed more easily. Tell someone in your specialist team if this happens.

Last reviewed: January 2016
Next planned review begins 2018