Cyproterone acetate

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.

Most prostate cancers need the hormone testosterone to grow. Testosterone is mainly made by the testicles. A small amount is also made in the adrenal glands. Cyproterone acetate stops the testicles from making testosterone. This reduces testosterone levels and may shrink the prostate cancer or stop it growing.

Cyproterone acetate may be given for a few weeks when you start taking hormonal drugs called LHRH agonists. This is to prevent a temporary rise in testosterone making symptoms worse (called tumour flare).

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.

These side effects happen to less than 10 in 100 people (less than 10%) who have this treatment. Some of them are much rarer than this but they are still important to know about. Rare means a side effect that happens to less than 1 in 1,000 people (less than 0.1%).

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.

You may feel slightly short of breath while you are taking this treatment. If this happens, tell your doctor, nurse or pharmacist. This should stop when the treatment ends.

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.

You may gain weight when you are having this treatment. Eating healthily and being active can help you keep to a healthy weight.

Sometimes weight gain can be caused by a build-up of fluid in the body. Your doctor, nurse, pharmacist or dietitian can give you more advice and treatment to help.

This treatment may cause swelling and tenderness of your breast tissue. This is called gynaecomastia. To prevent this, some people have 1 or more low-dose radiotherapy treatments to the chest before treatment starts. Another type of hormonal drug might be used to treat the breast swelling. Your doctor can give you more advice.

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 may last up to 5 minutes. You might also have sweats or feel anxious or irritable during a hot 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.

This treatment can affect how the liver works. You will have regular blood tests to check this. Sometimes liver changes can be serious. Contact the hospital straight away on the 24-hour number if you have any of these symptoms:

• yellow skin or eyes
• feeling very sleepy
• dark urine (pee)
• unexplained bleeding or bruising
• pain in the right side of your tummy (abdomen).

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.

While you are having this treatment, there may be changes to how your hair grows. For example, the hair on your head might become thicker or thinner, or you may lose some body hair. Your hair may also be drier, more brittle than usual, or change colour.

If you are worried about this, talk to your nurse about hair care.

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.

When this treatment is taken for a long time, there is a very rare risk of developing a type of brain tumour called a meningioma. Your cancer doctor or specialist nurse can give you more information.

If you have diabetes, this treatment may make your blood sugars higher than usual.

Signs of raised blood sugar include:

• feeling thirsty
• needing to pass urine (pee) more often than usual
• feeling more tired than usual.

You may need to check your blood sugar level more often, or make changes to your diabetic treatment. Your diabetic doctor or nurse will talk to you about how to manage this.

This treatment can reduce the number of red blood cells in your blood. Red blood cells carry oxygen around the body. If the number of red blood cells is low, this is called anaemia. You may feel:

• very low in energy
• breathless 
• dizzy and light-headed. 

If you have these symptoms, contact the hospital straight away on the 24-hour number. You may need treatment for anaemia. If you are very anaemic, you may need a drip to give you extra red blood cells. This is called a blood transfusion.

Taking this treatment for several months or more can increase the risk of bone thinning. This is called osteoporosis. It can make you more likely to get a broken bone (fracture). 

You may have bone density scans to check your bone health before and during treatment. These scans can diagnose osteoporosis or osteopenia (low bone density) so that it can be monitored. If your scan shows osteoporosis, your doctor usually prescribes:

• drugs to protect your bones called bisphosphonates
• calcium and vitamin D supplements. 

Regular exercise where you support your body weight, like walking, running and dancing, can help look after your bones. This is called weight-bearing exercise. Other types of strength exercises are also helpful. If you have any bone thinning or the cancer is affecting your bones, get advice from your cancer team first. 

Eating a healthy diet and not smoking also helps take care of your bones.