Side effects of radiotherapy for brain tumours

You might feel tired during your treatment. It tends to get worse as the treatment goes on. You might also feel weak and lack energy. Rest when you need to.

Tiredness can carry on for some weeks after the treatment has ended. But it usually improves gradually.

Various things can help you to reduce tiredness and cope with it, such as exercise. Some research has shown that taking gentle exercise can give you more energy. It's important to balance exercise with resting.

Get tips on coping with tiredness

Somnolence syndrome

In a few people, tiredness can become very severe within 5 to 6 weeks after the treatment finishes. This is called somnolence syndrome. You might also have other symptoms such as loss of appetite. 

Somnolence syndrome is more common in children, but can also happen in adults. It doesn't need treatment and gets better on its own over a few weeks.

Radiotherapy to the brain can cause hair loss or thinning. If you are having treatment to a particular part of the head, your hair usually falls out in that area. You might also have some hair loss on the opposite side of the head, where the radiotherapy beams pass through. This area is called the exit site.

Whether or not your hair grows back depends on the type of radiotherapy you're having. For example, if you're having radiotherapy to treat your symptoms, it's likely that your hair will grow back. Whereas treatment to try to cure your cancer uses a high dose of radiation and so permanent hair loss is much more common. 

You might like to cover your head with a soft hat, scarf or wig until your hair grows back. 

Find out more about head coverings and get tips on how to wash your hair during radiotherapy

You might feel sick during treatment and for a few weeks after the treatment has finished. Sickness is usually well controlled with medicines. Your treatment team can give you anti sickness tablets. Some people find that it helps to take them 20 to 60 minutes before having treatment.

Your doctor might also give you steroids. Radiotherapy to the brain can cause swelling which can lead to nausea. Steroids can help to reduce swelling and sickness.  

Read more about sickness

Radiotherapy for brain tumours can sometimes make symptoms worse before they get better. This is because the treatment can cause swelling in the brain. The swelling increases the pressure in the head and makes the symptoms worse.

This can be frightening because you might think the radiotherapy isn't working. Increased pressure in the brain might cause:

• headaches

• feeling sick

• fits (seizures)

You usually take steroids during treatment to help with this. 

Find out more about why your symptoms get worse during radiotherapy

Radiation can cause changes in the brain tissue. Blood vessels may slowly become scarred and blocked, reducing the blood supply to some areas of the brain. This can have an effect on your brain function. Symptoms of this include: 

• problems thinking clearly

• difficulty managing tasks that you previously found easy

• poor memory

• confusion

• headaches similar to migraines that come and go (this is sometimes called the SMART syndrome)

You might also have symptoms similar to those you had when you were first diagnosed.

Your doctor may suggest that you have an MRI scan or a PET scan to find out whether your symptoms are caused by changes in the brain tissue or by tumour cells.

Over a period of time, the treated area might develop a small area of dead cells. This is called radiation necrosis.

Radiation necrosis usually happens 1 to 3 years after the treatment finishes. It is more common in people who have had a high dose of radiation to a small area of the brain (radiosurgery). 

Most people don't have symptoms and do not need treatment. A small number of people might develop symptoms that depend on the area of the brain affected. If this is the case, you may have treatment with steroids or an operation to remove the affected area.

You might have changes in the levels of certain hormones if you have had treatment near your pituitary gland. 

For example, you might have thyroid problems or low levels of the hormone cortisol. You usually have blood tests to check for this. Your doctor can give you replacement hormones to take if you have changes in the levels of hormones.

In very rare cases, you may develop another brain tumour many years after you were first treated. This is because, although radiation kills cancer cells, it is also a risk factor for developing them. 

Unfortunately, tumours caused by previous radiotherapy tend not to respond very well to treatment. The tumours might be high grade and grow more quickly.

Talk to your treatment team if you are worried about developing a second cancer in the future.

You might develop a cataract in the lens of your eye if you have radiotherapy close to your eye. Cataracts can make your vision cloudy, blurred or dim.

You can usually have a small operation to treat cataracts.