Toremifene (Fareston®)

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

Many breast cancers rely on the hormone oestrogen (or estrogen) to grow. This is called oestrogen-receptor positive (ER positive) breast cancer. Toremifene blocks oestrogen from reaching the cancer cells. This means the cancer may grow more slowly. Or it may stop growing altogether.

We explain the most common side effects of this treatment here. We also include some that are less common.

You may get some of the side effects we mention, but you are unlikely to get all of them. And you may have some side effects, including rarer ones, that we have not listed here. 

Other cancer treatments may cause different side effects. If you are also having other cancer treatment, you may have other side effects.

When you have this treatment, you will have regular appointments with a doctor, nurse or pharmacist. Always tell them about any side effects you have. They can give you: 

• drugs to help control most side effects 
• advice about managing side effects. 

Most side effects can be managed. But sometimes side effects are harder to control. It is important not to stop taking hormonal therapy without telling your doctor. If side effects cannot be managed, your doctor may suggest a different type of hormonal therapy.

Some cancer treatments can cause serious side effects. Sometimes, these may be life-threatening. Your doctor, nurse or pharmacist can explain the risk of these side effects to you.

Your doctor, nurse or pharmacist will give you 24-hour contact numbers for the hospital. If you feel unwell or need advice, you can call at any time of the day or night. Save these numbers in your phone or keep them somewhere safe.

You may have a white or yellowish vaginal discharge when taking this treatment. Or you may bleed from the vagina. If bleeding continues for more than a few days, tell your doctor or nurse.

This treatment can cause a build-up of fluid in the body. This will slowly get better after treatment ends. Contact the hospital on the 24-hour number if you:

• are gaining weight 
• have swelling in your face, legs or ankles.

They can give you advice and treatment to help.

Feeling tired is a common side effect. Try to pace yourself and plan your day so you have time to rest between activities.

Being physically active can help to manage tiredness and give you more energy. It also:

• helps you sleep better
• reduces stress
• improves your bone health.

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

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 make you feel dizzy. Rarely, it causes blurred vision or changes in eyesight. Always tell your doctor or nurse if you have any of these side effects. If you feel dizzy or have changes in your sight, do not drive or operate machinery.

You may feel low or depressed, or have mood swings, during this treatment. Talking to family and friends about how you feel might help. If mood changes last for more than a few weeks, tell your doctor, nurse or pharmacist. They can talk to you about different ways to manage low mood or depression.

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.

Cancer and some cancer treatments can increase the risk of a blood clot. Contact the hospital straight away on the 24-hour number if you have any of these symptoms during or after treatment:

• throbbing pain or swelling in a leg or arm
• reddening of the skin in the area – if you have black or brown skin, this can be harder to notice, but the skin might become darker
• suddenly feeling breathless or coughing.

Always call 999 if you have:

• chest pain
• difficulty breathing.

A blood clot is serious, but it can be treated with drugs called anticoagulants. These thin the blood. Your doctor, nurse or pharmacist can give you more information about preventing and treating blood clots.

If you have been through menopause and take toremifene over a long period of time, you may have a slightly increased risk of cancer of the womb. The benefits of taking toremifene outweigh this risk. Your doctor may arrange for you to have tests each year to check your womb. If tests do find womb cancer, early treatment is very successful.

If you have vaginal bleeding after the menopause, tell your doctor. They can check for the cause. It can be an early sign of womb cancer, but it is usually caused by conditions other than cancer.

This treatment might increase certain risk factors for heart problems. Tell your doctor if you have:

• had any problems with your heart
• high blood pressure
• high levels of cholesterol – a fatty substance in your blood. 

They can monitor or treat these if needed. Talk to your doctor if you are worried about this. 

Things you can do to take care of your heart include:

• not smoking
• maintaining a healthy weight 
• being physically active.

This treatment may affect how your liver works. This is usually mild and goes back to normal after treatment ends. You will have blood tests to check how well your liver is working.