Fulvestrant (Faslodex®)

Hormones are chemicals that our bodies make. Hormones act as messengers and help control how cells and organs work. Hormonal therapies are drugs that change the way hormones are made or how they work in the body.

Many breast cancers need the hormone oestrogen to grow. This is called oestrogen-receptor positive (ER positive) breast cancer. These cancers have receptors (proteins) on the cancer cells that allow oestrogen to attach to the cell.

Fulvestrant blocks the receptors and stops oestrogen reaching the cancer cells. This slows down or stops the cancer cells from growing. Fulvestrant also reduces the number of receptors on the breast cancer cells.

Fulvestrant is given as an injection into a muscle (intramuscular).

You are given fulvestrant as 2 injections, one in each buttock. Each one takes 1 to 2 minutes.

The first 3 doses are given 2 weeks apart. After that you have the injections once a month. You may have the injections at the hospital, at your GP surgery, or at home. Your GP, specialist cancer nurse or practice nurse will give you the injection. If you are not able to visit the surgery, a district nurse may give you the injections at home.

If you sometimes delay the injections by 1 or 2 days, this should not affect how well the treatment works. But it is important to make sure you have your injections every month as prescribed.

Tell your doctor or nurse if you are taking any medicines to thin your blood, as this may increase bruising.

Your nurse or doctor will talk to you about your treatment plan. You usually have fulvestrant for as long as it helping to control the cancer.

You may have some pain, swelling, redness or a darker colour around the area that was injected. Let your doctor know if this happens. Painkillers may help.

This treatment might cause an allergic reaction. But this is not common. Signs of a reaction can include:

• a skin rash or itching
• feeling breathless or wheezy
• swelling of your face, mouth or throat.

If you feel unwell or have any of these signs, contact the hospital straight away on the 24-hour number. Do not take any more of this treatment until you have checked with them.

Always call 999 if swelling happens suddenly or you are struggling to breathe.

Hot flushes are a common side effect of this treatment. During a flush, your neck and face may feel warm. If you have white skin, your skin may look red. If you have black or brown skin, your skin colour may deepen. Flushes can last up to 5 minutes. You might also have sweats or feel anxious or irritable during a flush. 

Here are some things you can do to reduce the effects of hot flushes:

• Wear natural fabrics, such as cotton.
• Wear layers so you can remove clothes as needed. 
• Use cotton sheets and layers of bedding you can remove. 
• Try cooling pads or pillows to keep you cool.
• Keep rooms cool or use a fan.
• Have cold drinks and avoid caffeine and alcohol. 

You might have fewer hot flushes as your body adjusts to this treatment. You could try therapies to help you cope with hot flushes, such as:

• talking therapies like cognitive behaviour therapy (CBT)
• controlled breathing exercises
• yoga
• acupuncture. 

If they do not improve, talk to your doctor. Certain drugs can help to improve hot flushes. 

Flushes usually stop a few months after treatment ends. But some people continue to have them.

You may feel sick, but this is usually mild. If you feel sick, tell your doctor or nurse. They can give you anti-sickness drugs to help.

You may get pain in your muscles or joints. If this happens, tell your doctor or nurse. They can give you advice and painkillers or other drugs to help. Being physically active and keeping to a healthy weight may help with the pain. It can keep your joints flexible and reduce stress on them. If the pain does not get better, tell your doctor or nurse. They may talk to you about changing to a different hormonal drug.

This treatment can affect your skin. It may cause a rash, which may be itchy. Your doctor or nurse can tell you what to expect. If your skin feels dry, try using soap-free cleansers and unperfumed moisturising cream every day. 

Always tell your doctor or nurse about any skin changes. They can give you advice and may prescribe creams or medicines to help. Changes to your skin usually improve when treatment ends.

This treatment may affect how your liver works. This is usually mild. You will have blood tests to check how well your liver is working.

This treatment may cause diarrhoea. Diarrhoea means passing more stools (poo) than is normal for you, or having watery or loose stools. You may also have stomach cramps. If you have a stoma, it may be more active than usual. 

If you are passing loose stools 3 or more times a day and this is not normal for you, contact the hospital as soon as possible on the 24-hour number. Follow the advice they give you about:

• taking anti-diarrhoea medicines 
• drinking enough fluids to keep you hydrated and to replace lost salts and minerals
• any changes to your diet that might help. 

They might also ask you for a specimen of your stool to check for infection.

This treatment may cause headaches. If you have headaches, tell your doctor, nurse or pharmacist. They can give you advice about painkillers that may help. Tell them if the headache does not get better, or gets worse.

Fulvestrant can make you more likely to get a urine infection. Let your doctor know if you have pain or discomfort when you pass urine, if you need to go more often or if your urine is cloudy or smelly. Your doctor may prescribe antibiotics.

Feeling tired is a common side effect of this treatment. It is often worse towards the end of treatment and for some weeks after it ends. Try to pace yourself and plan your day so you have time to rest. Gentle exercise, like short walks, can help you feel less tired. 

If you feel sleepy, do not drive or use machinery.

Some medicines can affect how this treatment works or be harmful while you are having it. Always tell your cancer doctor, nurse or pharmacist about any drugs you are taking or planning to take, such as: 

• medicines you have been prescribed
• medicines you buy in a shop, pharmacy or online
• vitamins or supplements 
• herbal drugs and complementary or homeopathic therapies
• recreational drugs – for example, cannabis.

Some preparations of this treatment contain alcohol. If having alcohol is a problem for you, tell your doctor, nurse or pharmacist. Your blood alcohol level may be above the legal limit after you have the treatment. Do not drive or operate machinery for a few hours after having this treatment, even if you feel okay.

Some cancer drugs can affect whether you can get pregnant or make someone pregnant. If you are worried about this, it is important to talk with your doctor before you start treatment.

You are advised not to breastfeed while having this treatment, or for some time after treatment ends. This is because the drugs could be passed to the baby through breast milk. 

Your doctor, nurse or pharmacist can give you more information.

If you need medical treatment for any reason other than cancer, always tell the healthcare professional that you are having cancer treatment. Give them the contact details for your cancer doctor or cancer team so they can ask for advice.

If you have appointments with a dentist, always tell them you are having cancer treatment. Talk to your cancer team before you have any dental treatment.