Radiotherapy

Radiotherapy uses radiation to destroy cancer cells. You may have it as part of your cancer treatment, depending on the type of cancer you have and how advanced it is. 

Radiotherapy does permanent damage to cancer cells – causing them to die or stop growing. Healthy cells nearby are also damaged, but these are usually able to repair themselves and get back to normal. 

Radiotherapy can be given to you externally or internally. You might have radiotherapy on its own, or with chemo (this is called ‘chemoradiation’). You might have it after surgery to reduce the risk of the cancer coming back (this is called ‘adjuvant’ radiotherapy) or you might have radiotherapy before surgery to shrink a cancer (this is called ‘neoadjuvant’ radiotherapy). Radiotherapy can also be used to improve the symptoms you’re experiencing.  

In external radiotherapy, machines are used to target cancerous cells with special X-rays. In internal radiotherapy, radioactive liquids and implants are used inside your body to attack cancerous cells. 

 As you might have already heard, there is lots of medical jargon that’s associated with cancer and its treatment. If you’re not sure what someone means it’s totally fine to keep asking questions until you do. 

External beam radiotherapy 

During external beam radiotherapy, you’ll need to stay still for a few minutes while high-energy radiation is targeted at your cancer and a small area of surrounding healthy cells, in case the cancer has spread. Your care team will help you with this, and talk you through everything you need to do. 

If you have external beam radiotherapy, you’ll be given lots of individual treatments. These are called fractions. 

The machine that’s used doesn’t touch you, you won’t feel any pain while you are having the treatment and you usually won’t need to stay in hospital overnight. 

There are other types of external radiotherapy too, which doctors use to target very specific areas, like proton beam therapy which you can find out more about here.   

If you need to have radiotherapy to your head or neck you might need to wear a radiotherapy mask. Find out more about what they are and how they’re fitted here. 

Internal radiotherapy 

Internal radiotherapy involves radioactive liquids and implants, such as radioactive iodine therapy. 

You might be given a liquid to drink, a tablet to swallow or an injection. This won’t cause any long-term harm, but you might need to stay in a hospital room by yourself for a few days while you become less radioactive. 

Implants are things like wires and tubes, put in your body to release radiation near cancer cells, then left in your body for between a few minutes and a few days – or sometimes for good. 

People often have five treatments a week, one a day Monday to Friday, with a chance to rest over the weekend and to let healthy cells recover. You might need treatment over the weekend too, although this is rare.  

In total, external radiotherapy usually lasts between one and seven weeks. 

If you have internal treatment, your doctors will let you know how long a radioactive implant will be left in for, or how often you need to visit hospital. You might need to stay in hospital after internal treatment. 

A lot of the common side effects of external radiotherapy are quite mild and don’t last too long, but they can still be unpleasant. 

Side effects of external radiotherapy can be: 

Sore skin 

You might find your skin gets red or darker. It might get dry and itchy too, or peel like you’ve spent too long in the sun. This usually heals in a couple of weeks. In the meantime, use unperfumed soap and don’t shave any skin that hurts. If it’s summer, you should keep covered up, and wear some sun cream (factor 30 or higher) on any exposed skin. If it’s winter, protect your skin from chilly winds by wearing layers and a scarf. 

Losing your hair 

Your hair might fall out in the area you’re having treated. So if you’re having treatment on your head or neck, there’s a good chance you’ll lose the hair on your head, and this can be tough. It might grow back thinner, or sometimes it might not grow back at all.  But this will just be where the radiotherapy has been directed – not all over. It’s worth asking the radiotherapy team about this before you start your treatment.  

Tiredness 

Your body uses a lot of energy to repair healthy cells that are damaged by radiotherapy and you might feel tired for weeks or months after treatment, so give yourself plenty of time to relax if you’re feeling wiped out.  

Sickness 

Most people aren’t sick during radiotherapy – it depends where the radiotherapy is being directed. It’s more likely if you’re having radiotherapy to your stomach or pelvis, but this usually stops a few days after your treatment. If you do feel rough, talk to your doctor, who will be able to give you some anti-nausea drugs. Diarrhoea can be a common problem too, and your doctor can also prescribe something to help with that. 

Not feeling hungry 

It’s not surprising, really – if you’re feeling sick and tired, eating’s never going to be the first thing on your mind. If you do find you’re not feeling hungry, try and keep your energy levels up by eating little and often. If you’re worried about your appetite or weight during your radiotherapy treatment you should speak to your care team.  

And some more radiotherapy side effects… 

Swallowing can hurt if you have radiotherapy to your throat. Your joints might become stiff where you’re being treated. And you might find you lose interest in sex. These are likely to get back to normal once your treatment ends but it may take some time. 

Long-term effects 

Sometimes, radiotherapy can have side effects that don’t get better once the treatment has finished. These vary depending on where your cancer is but, if you’re worried, talk to your doctor or nurse about possible long-term side effects before you start any treatment. 

There’s a chance you could still get side effects a long time after your treatment has finished. This doesn’t happen to everyone and it doesn’t mean your cancer is back. Find out more about late effects. 

Cancer and cancer treatment can be confusing. So never be afraid to ask questions. And if you don’t understand the answers you get, keep asking until you do.

If your doctor recommends radiotherapy as a treatment for you, you might like to ask:

• What kind of radiotherapy is being recommended?
• Why is it the best option?
• Will it be combined with other treatments?
• How long treatment will last?
• What the side effects might be, and how we can reduce them?
• What are the possible long-term effects?
• Will there be any physical impact of having radiotherapy? E.g. scarring 
• How effective is it likely to be?
• Are there other options which might work?

This page was reviewed in 2024. It will reviewed again in 2027.