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Side-effects of radiotherapy (adults)

You're likely to experience some side-effects when having radiotherapy. Some of these will be temporary and others may be long-term. The benefits of having radiotherapy far outweigh the risks.

Generally, radiotherapy is delivered as an outpatient procedure, so you'll likely need to go into hospital for each fraction and then go home afterwards.

Help with your check-up appointments

After having radiotherapy, you’ll have regular check-up appointments, but it can be difficult to remember every symptom or side-effect you’ve had since your last appointment. Use BRIAN’s quality-of-life tracker to record these, then share this with your healthcare team.

Help with your check-up appointments

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What are the typical immediate side-effects of radiotherapy?

Generally, the more immediate side-effects will gradually disappear within around 6-12 weeks after treatment finishes. Common side-effects of radiotherapy include:

Tiredness and feeling fatigued

It‘s very common to feel tired during your treatment. As the weeks of radiotherapy go on, you may feel increasingly more so. This may be because your body is using its resources to repair any damage to healthy cells caused by the radiotherapy.

It may also be because of all the journeys you’re making to and from the hospital.

Unfortunately, the feeling of tiredness doesn’t immediately stop once the treatment stops and may continue for a number of weeks afterwards.

Some people can get a rare side-effect where, a few weeks after treatment has finished, their tiredness becomes severe. This is called somnolence syndrome. However, it usually gets better on its own over a few weeks without any treatment.

Occasionally, some people will have a delayed onset of fatigue, up to five years after radiotherapy treatment. You can contact your GP or healthcare team if this happens to you.

Hair loss

Unfortunately, you will lose some hair during radiotherapy, and this can be quite distressing.

Generally, your hair will only be lost from the places where the radiotherapy beam enters and leaves your head. If, however, you have whole brain radiotherapy, you're likely to lose hair from your whole head. You can talk to your radiographer about where you're most likely to lose hair.

Knowing that there'll be some hair loss means that you can plan ahead. Take a picture of how you usually wear your hair, so that a hairdresser can shape a wig. You could also keep a lock of your hair to match the colour and texture.

Some people have found gradually cutting their hair shorter, or even shaving it all off, before the start of treatment can help it feel less of a shock.

Hair loss usually starts around three weeks after treatment starts. Most hair loss is temporary, and will begin to grow again two or three months after finishing treatment.

Re-growth is often not as thick as it was before, and your hair may not be the same colour or texture. For example, it may be curly, when it was straight before. For some people, hair loss can be permanent.

There are many styles of wig that you can choose from, including synthetic (monofibre) and human hair wigs. And also lots of places that sell hats, bandanas or wigs and hairpieces as practical suggestions for coping with hair loss.

A list of organisations that sell wigs and other headwear is included in our downloadable information about radiotherapy.

You may be entitled to an NHS free synthetic wig.

My hair is part of my identity, so losing it really affected my confidence.

Emeline Gihooley

Read Emeline's story

Emeline Gilhooley, diagnosed with a grade 3 brain tumour in 2018, whose hair has now grown back

"It was mentioned that the radiotherapy might make me lose my hair, but not how much, as it’s different for everyone.

"By session 17, I was half bald, with a ‘reverse monk’ hairstyle. I felt very self-conscious, so took back some control and shaved it all off.

"There’s no quick fix to get your confidence back, but you can learn how to accessorise and style yourself. Treat yourself and find ways to make your new look seem purposeful. I bought lots of earrings: dangly, colourful, tasselled – as many colours and styles as I could find!

"My friends were very supportive and, if I told them I was having a crisis of confidence, they’d build me back up.

"I’ve had so many emotions, but I’ve had the chance to try new styles I wouldn’t have otherwise. Losing your hair will suck, there’s no denying it. But you aren’t alone and there are people you can talk to who understand what it’s like.

"Just learn what works for you, trust your instincts and talk to people – that’s the best thing you can do for yourself."

Join one of our Online Support Communities for more stories and tips about coping with a brain tumour diagnosis from people who know what you're going through.

Skin sensitivity

During or a few weeks after radiotherapy, some people develop changes to their skin in the area being treated, i.e. on your scalp. These can be like sunburn (red, blotchy and itching) in people with pale skin, and darkening of the skin in those who have darker skin.

As your skin will be more sensitive after radiotherapy, you should take care to protect it from strong winds and the sun. Always wear suntan lotion and a sunhat with neck protection when you're outside.

Usually, the sensitivity will fade in the month or so after treatment, but you should keep using high factor sunscreen long-term on the areas of the skin that have had radiotherapy. This is because radiotherapy can permanently destroy the pigment producing cells in your skin. These cells enable you to tan and protect you from sunlight damage and developing skin cancer.

Your health team will be able to give you further guidance if you develop skin sensitivity.

Nausea, vomiting and reduced appetite

If you have radiotherapy, especially targeted at the lower part of your brain, you may feel sick or actually be sick following treatment. This can start from around an hour after treatment and last some weeks. 

Your doctor can give you anti-sickness tablets (known as anti-emetics) to help manage nausea and vomiting. There are also some changes you can make to your diet to help manage this side-effect.

Reduced appetite

Fatigue, feeling nauseous and vomiting may make you temporarily lose your appetite during radiotherapy. This can lead to weight loss, which is not recommended for anybody receiving radiotherapy.

If you're struggling to maintain a healthy diet, you should speak to your healthcare team or dietitian. You could also make some changes to your diet to help you eat more.

Myelosuppression (slowing of the production of blood cells by the bone marrow)

Radiotherapy can temporarily slow the production of blood cells by the bone marrow. Low blood cell counts are usually not severe enough to cause major problems.

When there is a break from treatment for a few days, blood cell counts usually recover. However, the low levels can sometimes lead to anaemia, increased risk of infection and/or bleeding, such as bruising or nosebleeds.

If you've had radiotherapy to the brain and spine, or if you're also having chemotherapy, you're more at risk of these effects.

Worsening of symptoms

Radiotherapy to the brain can cause swelling in the treatment area. This swelling increases the pressure in the head, so can sometimes make symptoms worse before they get better.

Your doctor might give you steroids to try to prevent this. Your symptoms usually get better in time.

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Long-term side effects of radiotherapy

Radiotherapy is given in a way designed to limit the chance of permanent side-effects as much as possible. Very few people develop long-term difficulties.

Once the whole course of treatment is complete, you'll have regular check-up appointments to monitor the effects of your radiotherapy treatment. Generally, side-effects, apart from hair loss, will gradually disappear within around 6-12 weeks.

Occasionally, some side-effects can be longer-term or develop later in life. Your health team will talk through any side-effects with you before any treatment is given.

Long-term effects of radiotherapy could include impacts on:

​Cognitive skills

Cognitive skills include thinking, memory, learning, concentration, decision-making and planning. They also include processing skills, such as recognising and making sense of information from your senses, particularly sight and hearing. If a large part or the whole of your brain is treated, there is a long-term risk of cognitive impairment. Read more about cognition and brain tumours.


If the radiotherapy is delivered near to your eyes, there's a chance of developing a cataract in the lens of the eye several months or even years later. Cataracts can make your vision cloudy, blurred or dim. However, they can usually be easily treated with a simple, small operation. Read more about sight problems and brain tumours.

Hormonal effects

Radiotherapy treatment that includes the pituitary gland at the base of the brain can affect the production of the various hormones that the pituitary controls.

This can cause a variety of symptoms related to functions such as body temperature, growth, salt and water balance, sleep, weight and appetite.

As part of your follow-up after radiotherapy, you may have blood tests to check your hormone levels, but if you notice any new symptoms, you should discuss them with your doctor.

Second tumour

Radiotherapy can cause changes that, over a long period, can lead to a second tumour developing.

However, the benefits of having radiotherapy far outweigh the risks.

Only a small number of people will develop a second cancer because of the treatment they've had.

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