What is radiotherapy?

Radiotherapy means the use of radiation, usually x-rays, to treat cancer. You might have radiotherapy from inside the body, called internal radiotherapy. Or external radiotherapy, which is from outside the body. 

You may have radiotherapy:

  • to try to cure cancer
  • reduce the chance of cancer coming back
  • to help relieve symptoms

You might have it by itself or with other treatments, such as chemotherapy or surgery.

Most types of radiotherapy use photons. But you might have electrons or more rarely protons. Your doctor decides which type you need.

How radiotherapy works

Radiotherapy is a type of ionising radiation (high energy) that destroys cancer cells in the treated area by damaging the DNA  Open a glossary itemof these cells. Radiation also affects normal cells. This can cause side effects in the treatment area.

Usually the side effects improve a few weeks after treatment. But some might continue long term. Your doctor will talk this through with you before you start treatment. They will also discuss possible ways of managing side effects.

Aim of radiotherapy treatment

Your radiotherapy treatment plan is individual to you.

It aims to give a high dose of radiation to the cancer but as low a dose as possible to the surrounding healthy cells. This gives the highest chance of curing or shrinking the cancer, while reducing the risk of side effects.

Your course of treatment

When deciding on your course of treatment your doctor takes into account:

  • your type of cancer
  • the position of the cancer in your body
  • any other treatment you've had, are having, or is planned for you
  • your general health and fitness

Radiotherapy with the aim of curing cancer usually lasts between 1 to 7 weeks.

For radiotherapy to relieve symptoms, you might have anything between a single treatment to 2 weeks of treatment. It might be longer than this. Your doctor will tell you how many treatments you’ll have. 

Most people have daily treatment from Monday to Friday, with a rest at weekends. But this can vary. For example, you might have treatment once a week for a set number of weeks. It is also sometimes possible to have more than one treatment per day.

Let your therapeutic radiographer know if you have any commitments, such as work or childcare, that mean you need a specific time for your appointments. They will try to be as flexible as possible, but it can be difficult depending on how busy the department is.

Worries about treatment

You may feel anxious about radiotherapy and this is normal. It can help to talk through any worries you have with your doctor, nurse or radiographer.

  • Devita, Hellman and Rosenberg's Cancer: Principles and Practice of Oncology (12th edition)
    VT Devita, TS Lawrence and SA Rosenberg
    Wolters Kluwer Health, 2023

  • External Beam Therapy (Radiotherapy in Practice) Third Edition
    Peter Hoskin
    Oxford University Press, 2019

  • Cancer and its Management (7th edition)
    J Tobias and D Hochhauser
    Wiley Blackwell, 2015

  • Walter and Miller's Textbook of Radiotherapy: Radiation Physics, Therapy and Oncology (8th edition)
    R Symonds, J A Mills and A Duxbury
    Elsevier, 2019

  • Practical Radiotherapy Planning (5th edition)
    S Morris, T Roques, S Ahmad and S Loo 
    CRC Press, 2023

  • Radiotherapy in Practice - Brachytherapy
    P Hoskin and C Coyle
    Oxford University Press, 2011

Last reviewed: 
04 Oct 2023
Next review due: 
05 Oct 2026

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