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Radiotherapy is a treatment to destroy cancer cells with radiation. A beam of radiation is targeted on the cancer, which shrinks it.

Your care may differ from what is described here as it will be designed to meet your individual needs. It’s important that you discuss your radiotherapy treatment with your doctor.

Radiotherapy can treat many different types of cancer. About four out of 10 people who have cancer will have radiotherapy as part of their treatment.

Radiotherapy uses high-energy radiation, such as X-rays and gamma rays. It works by destroying the DNA inside cancer cells. This prevents them from reproducing and therefore shrinks cancerous tumours. Healthy cells will also be affected but they are usually able to repair themselves.

There are two main types of radiotherapy treatment – external radiotherapy and internal radiotherapy.

Radiotherapy is used for the following reasons.

  • To destroy the tumour. Radiotherapy can be used on its own or combined with other treatments such as surgery or chemotherapy. If the aim is to cure your cancer with radiotherapy, this is known as radical radiotherapy.
  • To reduce the size of a tumour before surgery. This is called neoadjuvant treatment.
  • To make sure all the cancer cells are destroyed after surgery. This is called adjuvant treatment.
  • To slow down the progress of the cancer, relieve pain and other symptoms. This is called palliative treatment and is used for advanced cancer.

The number and duration of radiotherapy sessions you have will depend on the type of cancer you have and where it is in your body. You may have one or two treatments with radiotherapy. However, you usually have a course of treatment over days or weeks.

A team of health professionals (a multidisciplinary team) will be involved in your radiotherapy treatment. These professionals will include a clinical oncologist (a doctor who specialises in cancer care using radiotherapy and chemotherapy) and a radiographer. A radiographer is a healthcare professional trained to perform imaging procedures.

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  • Preparation Preparing for radiotherapy

    If you smoke, it's a good idea to stop. Research has shown that giving up smoking may make radiotherapy more effective and reduce possible side-effects of the treatment.

    Your clinical oncologist will put a plan together before you start treatment. The plan will take into account the size of your cancer, how well it will respond to radiotherapy and the sensitivity of your surrounding tissues. He or she will also consider your general health and fitness.

    You may need to have tests to help find out the size and position of your cancer. These may include an X-ray, CT scan or MRI scan. Your healthcare team will then calculate how much radiation you need to treat your cancer and exactly where you need it.

    If you're having external radiotherapy, your healthcare team may use a special machine called a simulator to plan your treatment. This machine moves in the same way as that which will deliver radiotherapy. It will help your radiographer plan exactly how to position your body when you have radiotherapy.

    Your radiographer may tattoo a few tiny dots on your skin to help locate the exact spot when you have treatment. Occasionally, if you need to keep the area very still, he or she may make a mould. For example, if you're going to have treatment on your head and neck, you may need to wear a see-through plastic mask or brace. This will make sure your head remains in exactly the same position for each treatment.

  • The procedure What happens during radiotherapy?

    External radiotherapy

    External radiotherapy delivers radiation to you from an external source. There are a number of techniques for doing this.

    One technique is to use a machine known as a linear accelerator. This produces high-energy beams of radiation, either as X-rays or gamma rays. Your radiographer will ask you to sit or lie down in a fixed position. It's important for your radiographer to position the radiotherapy equipment accurately to target the beam of radiation exactly on the right spot.

    The machine may then rotate around you, or it may be fixed in one position. The machine won't touch you at any point but it can be quite noisy, with whirring and buzzing sounds. Your radiographer will leave the room during your radiotherapy. There is an intercom so you can communicate with him or her at all times.

    Other types of external radiotherapy use imaging scans, such as CT scans, and computer technology to map the position of the cancer in your body. This helps to deliver the radiotherapy to the cancer and protects your surrounding tissues better than conventional techniques.

    There are also forms of very targeted higher dose radiotherapy, such as gamma knife. These are used for specific types of cancer but may involve just a few treatments at a higher dose than standard radiotherapy.

    The type of external radiotherapy you have will probably depend on where your cancer is. Ask your radiographer for more information.

    External radiotherapy won't make you radioactive during or after the treatment because no radiation-producing material gets inside your body. You may be able to carry on with many of your usual daily activities. However, you may feel tired during and after your treatment. It's a good idea to ask friends and family for help and support if you need it.

    Internal radiotherapy

    In internal radiotherapy, the source of radioactivity will be put inside your body so it can get closer to the cancer. This can be done in two main ways.


    In brachytherapy, a doctor or surgeon will put a solid source of radiation within, or next to, your cancer tumour to give you radiotherapy. This harms healthy tissue around the cancer as little as possible.

    You can have either temporary or permanent brachytherapy. The type you have will depend on what type of cancer you have.

    If you're having temporary brachytherapy, the source may be left in place for anything from a few minutes to a few days. If you're a woman and have a gynaecological cancer, such as cervical cancer, the radiation source will be placed inside your vagina during the treatment. For other cancers, you may need to have a minor operation under general anaesthesia to put the radioactive source into your body.

    You may need to stay in hospital for a day or two after your treatment. Your visitors will be restricted because you will be radioactive while the source is in place.

    If you're having permanent brachytherapy, your surgeon will place tiny radioactive implants inside your body that will stay in place. For example, if you're having treatment for prostate cancer, your surgeon will place small radioactive pellets, known as seeds, into your prostate gland. These will deliver a steady dose of radiation to the prostate. You won't be a risk to others from radiation because the implants only produce a very small amount of radiation. They gradually lose their radioactivity over time.

    Radioisotope therapy

    In radioisotope therapy, a radioactive substance (a radioisotope) is used to treat your cancer. You can have it as an injection into a vein, or directly into the cancer. You can also swallow capsules or drink a liquid. Radioisotope treatment is often used to treat thyroid cancer.

    After radioisotope therapy, your body will give off small amounts of radiation. You may need to stay in hospital for some time after treatment. After that you will need to take precautions to minimise the risk to other people from any radiation. For example, don't get close to pregnant women or children for several days afterwards. The radioactive material will leave your body in your body fluids, such as sweat and urine. Therefore, your healthcare team may advise you to flush the toilet twice after each use for example.

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  • Recovery Recovering from radiotherapy

    After your treatment, your clinical oncologist will arrange a follow-up appointment. He or she will check how you're recovering from any side-effects and what your response has been to the radiotherapy. This is a good opportunity to discuss any concerns or to ask about any long-term side-effects that you might expect to have after your treatment.

    Patient groups can give you support and advice on recovering after radiotherapy.

  • Risks What are the risks?


    Side-effects are the unwanted but mostly temporary effects you may get after having the treatment. They can vary greatly depending on what part of your body is treated and the type and dose of radiotherapy you have. Unlike chemotherapy, the side-effects of radiotherapy mainly affect the part of your body being treated. Your healthcare team will give you information about the side-effects of your specific treatment before it starts.

    Possible side-effects immediately after radiotherapy may include:

    • tiredness
    • loss of appetite
    • feeling sick and vomiting
    • diarrhoea
    • red, sore or itchy skin
    • coughing and shortness of breath
    • a dry mouth or sore throat, which makes it difficult to swallow
    • hair loss – usually temporary but it can be permanent (this only happens in the area being treated)
    • emotional symptoms – feeling low, depressed or anxious after treatment
    • stiffness of joints and muscles

    Radiotherapy can also cause long-term side-effects such as:

    • darkening of your skin
    • swelling of your arms and legs
    • shortness of breath – if you have had radiotherapy to your chest
    • infertility – if your ovaries or testicles are within the treatment area
    • memory loss
    • problems going to the toilet or with sex (if you had radiotherapy on your pelvis)

    It's possible that radiotherapy can cause a second cancer to develop several years after treatment. The benefits of the radiotherapy generally outweigh this risk but you may wish to discuss this with your doctor.

  • FAQs FAQs

    Can radiotherapy be used together with surgery or chemotherapy?


    Yes, many cancers are treated with a combination of surgery, chemotherapy and radiotherapy.


    Some cancers can be effectively treated with just one type of treatment – surgery, chemotherapy or radiotherapy. Others need a combination of two or all three types. For instance, if you have surgery to remove a cancerous breast lump, you may have radiotherapy to your remaining breast tissue or chest wall. This will help reduce the risk of cancer coming back in nearby tissues. You might then also have some chemotherapy to reduce the risk of cancer spreading to other parts of your body.

    For certain cancers, you may take chemotherapy medicines at the same time as having a course of radiotherapy. This is known as chemoradiation. It's used to treat anal cancer and some oesophageal cancers.

    What can I do about the side effects of radiotherapy?


    The side-effects of radiotherapy are often short-term and there are treatments for them.


    Common side-effects of radiotherapy include tiredness, red and sore skin, and stomach problems, such as feeling sick and diarrhoea.

    There is no specific treatment for tiredness. However, it may help to be well prepared for a course of radiotherapy. For example, it can help to get an understanding of how you might feel and the need for some extra rest.

    If you have irritated skin, don't use creams or powders unless they have been prescribed by your radiographer because they may make it worse. Wear loose-fitting clothes to help reduce irritation too. After radiotherapy your healthcare team may put special dressings on your skin to help. Your skin may be more sensitive to the sun after radiotherapy so take care in the sun.

    It's important to eat and drink well during your treatment. Your cancer care team will give you specific advice about how to get enough fluids and nutritious food during your treatment. You may need to take food supplements, such as high-calorie soups and milkshakes. If you lose a lot of weight, your doctor may need to insert a feeding tube temporarily.

    A sore mouth is a common side-effect of treatment for head and neck cancers. If you have this, an aspirin-based mouthwash may relieve it.

    As well as good dietary support, there are medicines to help prevent and treat diarrhoea and vomiting. Ask your doctor for more information.

    Will radiotherapy affect my fertility?


    Infertility (not being able to become pregnant or father children) is only likely if your womb, ovaries or testicles are exposed to radiation.


    How radiotherapy will affect your fertility is influenced by factors including:

    • the type of cancer you have (and where you're having treatment)
    • the dose and duration of radiotherapy

    Discuss the risk of infertility with your doctor before you start your treatment. Radiotherapy to your pelvic area in women of childbearing age will usually bring on an early menopause. Your ovaries will stop producing eggs and female sex hormones. The lack of hormones will trigger the menopause, and you won’t be able to get pregnant afterwards. You may wish to consider hormone replacement therapy (HRT) to treat any symptoms of the menopause.

    Radiotherapy to the testicles or pelvis in men is likely to affect sperm production. This may lead to temporary or permanent infertility. Lower doses may interrupt sperm production for months or years. Higher doses will stop your sperm production permanently. If you wish to father children and have a normal sperm count before treatment, you may be able to freeze your sperm. This can be stored until you're ready to father a child.

    Discuss your fertility options with your doctor.

  • Resources Resources

    Further information


    • Radiation therapy for cancer. National Cancer Institute., published 30 June 2010
    • About radiotherapy. Cancer Research UK., published 2 July 2012
    • What is radiotherapy? Public Health England., published 7 November 2013
    • General principles of radiation therapy. Medscape., published 18 September 2013
    • Radiation therapy. The Merck Manuals., published September 2013
    • Radiation therapy principles. American Cancer Society., published 18 December 2012
    • Preparing your radiotherapy plan. Cancer Research UK., published 4 January 2013
    • Understanding radiation therapy: a guide for patients and families. American Cancer Society., published 24 January 2013
    • What to know about external beam radiation therapy. National Cancer Institute., published April 2010
    • The role and development of afterloading brachytherapy services in the United Kingdom. Royal College of Radiologists., published September 2012
    • Viswanathan AN, Thomadsen B. American Brachytherapy Society consensus guidelines for locally advanced carcinoma of the cervix. Part I: general principles. Brachytherapy 2012; 11(1):33–46. doi:10.1016/j.brachy.2011.07.003
    • Follow up after radiotherapy. Cancer Research UK., published 4 January 2013
    • Radiotherapy and your skin. Cancer Research UK., published 4 January 2013
    • Swallowing after head and neck radiotherapy. Cancer Research UK., published 4 July 2012
    • Stomach or pelvic radiotherapy side effects: sickness and weight loss. Cancer Research UK., published 4 July 2012
    • Fertility and cancer: what are my options? American Cancer Society., published 19 November 2012
    • Effects of radiotherapy on fertility. Macmillan Cancer Support., published 1 May 2013
    • Breast cancer treatment and management. Medscape., published 14 October 2013
    • Chemoradiation for anal cancer. Cancer Research UK., published 27 June 2012
    • Chemoradiation for oesophageal cancer. Cancer Research UK., published 7 September 2012
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