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Key points

  • Radiotherapy is a treatment to destroy cancer cells with radiation.
  • About four out of 10 people who have cancer will have radiotherapy as part of their treatment.
  • There are two main types of radiotherapy treatment – external radiotherapy and internal radiotherapy.
  • Possible side-effects of radiotherapy include tiredness and red, sore skin.

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.

About radiotherapy

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.

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.

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.

Radiographers preparing a man for radiotherapy, with the man lying on the table.
                                                      External radiotherapy

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.

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.

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.

Reviewed by Rachael Mayfield-Blake, Bupa Health Information Team, January 2014.

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  • This information was published by Bupa's Health Information Team and is based on reputable sources of medical evidence. It has been reviewed by appropriate medical or clinical professionals. Photos are only for illustrative purposes and do not reflect every presentation of a condition. The content is intended only for general information and does not replace the need for personal advice from a qualified health professional. For more details on how we produce our content and its sources, visit the about our health information page.

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