Expert reviewer, Christos Mikropoulos, Clinical Oncologist at Bupa
Next review due October 2023

Radiotherapy is a treatment for cancer that uses high doses of radiation to kill cancer cells. Over half of people who are treated for cancer have radiotherapy, often in combination with other types of treatment such as chemotherapy and surgery.

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About radiotherapy

In radiotherapy, high-energy radiation is targeted at the area of your body affected by cancer. The aim of radiotherapy is to target and destroy the cancer cells while avoiding damage to your healthy cells as much as possible.

You may have radiotherapy with the aim of curing your cancer. It can also be used alongside surgery. Sometimes this is beforehand, to make the tumour (growth of cells) easier to operate on; sometimes afterwards, to destroy any remaining cancer cells. If your cancer can’t be cured, your doctor may offer radiotherapy to help control your symptoms and improve your quality of life.

Types of radiotherapy

There are different types of radiotherapy. Here are the main ones.

  • External beam radiotherapy is the most common type of radiotherapy. Radiation is directed into the affected area of your body from outside your body, usually from a machine called a linear accelerator (linac).
  • Internal radiotherapy (brachytherapy) is when radiation is directed from inside your body. This involves placing radioactive implants near to or inside the affected area of your body.
  • Radioisotope therapy involves treatment with radioactive medicines, which you have either as an injection or as a liquid that you drink. The medicines target cancer cells in your body.

Which type of treatment you have depends on the type of cancer you have, and which part of your body is affected. Your radiotherapy will be designed for your particular circumstances and tailored to you. The following information looks at external beam radiotherapy and internal radiotherapy (brachytherapy) in more detail.

Preparing for radiotherapy

If your doctor recommends you have radiotherapy, they will discuss this with you and check whether or not you’re happy to go ahead. If you are, you’ll be referred to your nearest radiotherapy department. Not all hospitals have a radiotherapy department, so you may need to go to a specialist cancer hospital or a large regional hospital. You’ll usually start by seeing a radiation oncologist – a specialist cancer doctor who’ll plan and oversee your treatment.

External beam radiotherapy

If you're having external radiotherapy, you may be asked to come to the radiotherapy department for a CT planning scan to help plan your treatment. This is sometimes called ‘simulation’. Sometimes, you might be given special instructions about things you need to do before your scan. For instance, you may need an enema to clear your bowel or you may need your bladder to be full or empty.

Your radiotherapy team will want to take scans in exactly the same position that you’ll be in to receive your radiotherapy. They might use cushions and other equipment to support you. The team may tattoo tiny dots on your skin to show where the radiotherapy should be directed when you have your treatment. If you’re going to have radiotherapy to your head or neck, you might be fitted with a special plastic mask. This will hold your head in the right position while you have your treatment.

It may take up to a couple of weeks to plan treatment with external beam radiotherapy after having your scan.

Sometimes, instead of having a planning scan beforehand, your doctor may take X-rays or CT scans at the start of each of your radiotherapy sessions. This is known as image-guided radiotherapy. It helps your doctor ensure you’re in the best position and they can target the right area more accurately, giving better results and fewer side-effects. Sometimes, your doctor may implant ‘seeds’ before you begin your radiotherapy. This can help to show up the target area on X-ray during treatment.

Internal radiotherapy (brachytherapy)

If you’re having internal radiotherapy (brachytherapy), you’ll be asked to have a scan beforehand. This is so your doctor can work out how much radiation you need and where to put the implants. With internal radiotherapy, you can sometimes have the treatment on the same day as your scan.

What happens during radiotherapy?

External beam radiotherapy

External beam radiotherapy is most often given in small amounts (called fractions) over a number of days or weeks. This is usually on weekdays, so you should get weekends off. You’re most likely to have treatment as an outpatient, rather than staying in hospital. The whole session usually takes no more than around 20 minutes, including the time it takes to get you in the right position.

You’ll have radiotherapy in a special treatment room with a large machine called a linear accelerator (linac). You’ll be asked to lie in a certain position – usually the same as how you lay in your planning scan. The radiographers, who deliver the radiotherapy treatment, will help you to get in the right position. Once you’re ready, the radiographers will leave the room and the treatment will be delivered. Your radiographers will be able to watch you, and you can communicate with them if you need to. Having the treatment usually only takes a few minutes.

Having radiotherapy doesn’t hurt, but you might find it uncomfortable staying in position while you’re having it. Your radiotherapy team will make every effort to make you as comfortable as possible.

Internal radiotherapy

If you’re having internal radiotherapy (brachytherapy), you may need to stay in hospital for a few days.

The implants might be delivered using a needle, a catheter (thin tube) or an applicator, depending on the part of your body being treated. The implant can be taken out straight away or it can be left in for a set amount of time. Occasionally, it may be left in permanently, but the radioactivity will gradually wear off.

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What are the side-effects of radiotherapy?

Radiotherapy affects people differently. For some people, the side-effects are mild whereas for others, they may be more severe. It can depend on what part of your body is being treated, the type of radiotherapy you have and how much, and your own health. Your radiotherapy team will do all they can to minimise your chance of getting side-effects, and to help you cope if you do get them.

General side-effects of radiotherapy can include:

  • problems with your skin (for example, dryness, redness, itching, blistering or peeling) – your doctor may recommend some emollients (moisturisers) or steroid creams that can help
  • feeling tired and weak – rest when you need to, but try to keep as active as you can
  • losing your hair in the area that’s being treated – this is usually only temporary

Some side-effects may be specific to the part of your body that’s being treated. For instance, you may get:

  • dry mouth, difficulty swallowing and a sore mouth if you have radiotherapy to your head and neck
  • shortness of breath or an inflammation of the lung called pneumonitis if you have radiotherapy to your chest
  • nausea, vomiting and diarrhoea if you have radiotherapy to your tummy (abdomen)

Many of these side-effects do wear off but this can take several weeks.

Sometimes, radiotherapy can leave you with long-term side-effects. These might happen weeks or even years after you finish treatment, and there’s also a risk that the radiotherapy itself can cause another cancer. Radiotherapy to your lower abdomen or pelvis can affect your fertility.

Your doctor will give you more information about long-term side-effects associated with the type of radiotherapy you’re having, how these may affect you. They will also let you know the options available to you.

Is there any follow-up after radiotherapy?

After you have finished radiotherapy, you’ll usually have a number of follow-up appointments with your specialist radiation oncologist. How many appointments you have and how frequently they occur will depend on your personal circumstances. For instance, what type of cancer you were receiving treatment for and your risk of side-effects. Your doctor may need to take some X-rays and do some tests to check how the treatment went, and they’ll go through these with you.

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Related information

    • Radiotherapy. The British Institute for Radiology., accessed 17 September 2020
    • Cancer care. Oxford handbook of general practice. Oxford Medicine Online., published online June 2020
    • Principles of radiation oncology. Oxford handbook of oncology. Oxford Medicine Online., published online October 2018
    • Radiotherapy activity across England. National Cancer Registration and Analysis Service (NCRAS). Public Health England, June 2017.
    • Radiotherapy. Patient., last reviewed 23 December 2015
    • What is internal radiotherapy? Cancer Research UK., last reviewed 15 February 2019
    • Having external radiotherapy. Cancer Research UK., last reviewed 28 December 2018
    • Planning your external radiotherapy. Cancer Research UK., last reviewed 21 December 2018
    • What is brachytherapy? Cancer Research UK., last reviewed 4 February 2019
    • General side effects of radiotherapy. Cancer Research UK., last reviewed 23 January 2019
  • Reviewed by Pippa Coulter, Freelance Health Editor, October 2020
    Expert reviewer, Christos Mikropoulos, Clinical Oncologist at Bupa
    Next review due October 2023