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Radiotherapy services

Using high energy X-rays to treat cancer 



Radiotherapy staff member talking to a patientRadiotherapy uses high energy X-rays (or similar rays) to treat cancer.

It damages your body’s cells in the treatment area, killing cancer cells but allowing your normal cells to recover.

Its side effects are usually only in the area that you are having radiotherapy treatment. 

Radiotherapy treatment and side effects will vary depending on which part of your body you are having treated. This page has general information about radiotherapy. Your treatment team can give you more information about your type of cancer and  treatment, and will support you during your radiotherapy.

There is information on this page about:

Agreeing to radiotherapy treatment

Before your appointment to plan your radiotherapy treatment, you will be asked to sign a consent form. This is so we know you agree to have the radiotherapy treatment.

Your radiographer will ask you to confirm that you agree to having radiotherapy during your first appointment. If you would like more information or have any questions you can ask the radiographer at this apppointment.

Planning appointment for your treatment

You will have a CT scan at your planning appointment. This is so we know where in your body we need to treat you.

The planning appointment will take place in either

This appointment can take about 1 hour.

For the CT scan you will need to remove some of your clothing and you will be given a gown to wear.

You will be asked to lie on the couch and the radiographers will move you into position. The couch will move slowly through the open scanner and back, you will not feel anything and nothing will touch you.

During the procedure we ask that you remain as still as possible and breathe normally.

At the end of the CT scan the radiographers will take some measurements and may ask your permission to make some small permanent marks on your skin using ink and a needle. These marks show the radiographers exactly where the radiotherapy treatment needs to be given.

Before you leave the department we will give you the appointments for your treatment and information about your treatment schedule. You can ask any questions you may have about your treatment.

Your radiotherapy appointment schedule

Your doctor will prescribe the total amount of radiation needed for your treatment. This amount is then split-up into smaller doses (called fractions) that are given over a period of days or weeks. Treatment is usually given each day Monday to Friday, and sometimes on a Saturday.

You might just have one visit or lots of visits over 6 to 7 weeks.

Your treatment will start around 2 weeks after your planning appointment.

On your first day of treatment your radiographer will explain your treatment and any possible side effects. Please ask them any questions.

Radiotherapy treatment takes place in the Cancer Centre at Guy’s Hospital, or Guy’s Cancer at Queen Mary’s Hospital.

Having radiotherapy

Before treatment you will need to change into a gown. You will be in the treatment room for about 15 minutes.

The radiographers will help you into the same position you were in for the scan during your planning session. They will then move the treatment machine into position. It will come close to you, but will not touch you.

The machine will move around you to treat from different angles. Each area takes around 1 to 3 minutes to treat, and you will have the same areas treated each day.

It is important that you keep still during your treatment and breathe normally. 

The radiographers will leave the room to switch the machine on. You will be alone in the room during treatment but the radiographers will be able to see you on a TV monitor.

If you need help, raise your arm and the radiographers will switch off the machine and return to the room to help you.

  • Other types of radiotherapy


    Brachytherapy, also known as internal radiotherapy works by treating the cancer cells from inside the body.

    The source of radiation is placed inside or next to your cancer, as the radiation does not travel far. Brachytherapy can be used to treat cancer on its own or in combination with other treatments.

    Your treatment is carefully designed for you. The number of treatments you have will depend on the type and size of the cancer.

    For some types of cancer, you will need to make daily trips to the hospital. For others, you will only need to come once. Your doctor will discuss with you how many treatments you need and any special precautions you may need to take. 

    Stereotactic radiosurgery

    Stereotactic radiosurgery is a very precise, non-invasive treatment (not putting any instruments into the body).

    It uses a high dose of radiation to target small areas of the brain. It can be focused on a very precise point so that it doesn’t damage surrounding healthy tissues.

    Your doctor will decide with you if this is the best treatment for you. The accuracy of the stereotactic radiosurgery allows radiotherapy to be given over a few sessions using a high dose each day.

    You will need to have several planning scans, MRI and CT so the doctor can plan your treatment accurately. Treatment usually starts within a few weeks of the planning scans. It can be given as an outpatient appointment meaning you will not need to stay in hospital


Side effects of radiotherapy

You may not have all the side effects listed here. It will depend on which part of the body you are having treated.

The radiographers will give you information about the side effects that you may have during and after your treatment. Possible side effects are

  • red, dry or itchy skin (usually only in the area you being treated)
  • hair loss
  • feeling very tired (fatigue)
  • finding it hard to poo (constipation)
  • having runny poo (diarrhoea)

Getting support with side effects

  • NHS has more information about side effects of radiotherapy.
  • Dimbleby Cancer Care has information on coping with hair loss. If you do not have a wig and would like one, please ask to be referred to the patient appliance department who will help you to choose and fit your wig.
  • Macmillan Cancer Support have a free booklet, Coping with fatigue, that might be helpful.
  • Cancer Research UK has information about caring for your skin.
  • If you have any changes to your bowel habits, tell the radiographers or nurses who will be able to help you manage this side effect.
  • Tell the radiographers if you are concerned about any other effects of your radiotherapy treatment. They will be able to help and support you.
  • Treatment support radiographers are available if you have a specific problem with your treatment or any side effects.

After radiotherapy

The side effects from radiotherapy may be worse about 7 to 10 days after you have finished treatment. Any side effects you have may continue to get worse during this period, and you may have side effects that you have not had before. The radiographers will explain this more and support you to manage any side effects.

Sometimes people feel anxious at the end of their treatment. You will need time to recover physically and emotionally.

Follow-up appointments

You will have a follow-up appointment between 2 and 6 weeks after your course of radiotherapy ends. This will be with a doctor at the cancer centre, or with the doctor who referred you for radiotherapy. You will be given details of how to make this appointment.

Skin care after treatment

Depending on your course of treatment, your skin may be red and sore, and you will need to continue to use a moisturiser. If your skin is broken, you will need to see the treatment support team for advice, and possibly a dressing. You may need to return to the department or visit your local GP practice nurse.

Carry on with the same skin care until your skin does not look red or feel sore, and then slowly introduce your usual washing routine. If your skin starts to feel sore again, go back to using warm water and try again after a week.

Diet and mouth care after treatment

If you changed your diet to cope with the side effects, continue with this for a couple of weeks. Slowly introduce foods that you stopped.

If your throat is sore, continue with the same mouth care that you used during your treatment. Eat soft food that is not too hot or spicy. Your taste buds may take 3 months or more to recover, and you may find that you have less saliva. It is important that you drink plenty of fluids each day.

Your radiotherapy team

Your radiotherapy team will be made up of radiographers, doctors and nurses who will all support you during your treatment.

A clinical oncologist is a doctor trained in the use of radiotherapy and chemotherapy.

A radiographer gives you your radiotherapy and will be able to help and advise you during your treatment.

Nurses carry out nursing procedures such as changing dressings and managing the clinics.

Student radiographers will be in the radiotherapy department as this is a teaching hospital. The students will be supervised by a radiographer. Please tell your radiographer if you do not want students to be at your appointments. Your wishes will always be respected.

Information and support

Many people find it hard to cope with what is happening to them and feel anxious or depressed. It can be helpful to know that most people find these feelings ease with time.

Try to discuss your concerns with the staff that are involved in your treatment, as well as your family and friends. Talking to other people can help you to find the answers to your questions.

Dimbleby Cancer Care and the Dimbleby Macmillan Support Centre will give you information and different kinds of support.

Watch a video about our radiotherapy village

  • The Radiotherapy Village, Guy's Cancer – video transcript

    Audio: Bright and airy music plays.

    Audio: A health professional says: "Patients told us that going to the basement for the radiotherapy treatment wasn't ideal."

    Visual: A hand presses the R button for the lift to the radiotherapy floor.

    Audio: The health professional says: "We're the first centre in Europe to have radiotherapy above ground level."

    Visual: The lift arrives in a light and spacious area with large windows and high ceilings. There are signs to the waiting area, patient changing rooms, the treatment suite and check-in. There is a corridor with a series of orange doors. The video ends with a health professional controlling a radiotherapy machine.


Ref number: 1767/VER8

Date published: May 2020 | Review date: May 2023

© 2021 Guy’s and St Thomas’ NHS Foundation Trust

A list of sources is available on request




Phone: 020 7188 7188 (ext 57542) or 
0207 188 3160

If you have a problem in the evening or weekend, please call the main switchboard, ask for 'operator' or dial 0. Then ask the operator for the clinical oncology registrar on call.

Other useful contacts

Cancer Centre at Guy's reception
Phone: 020 7188 7188 (ext 56805)
8am to 8pm, Monday to Friday

Cancer helpline for our current patients
0207 188 3754
8.30am to 6pm, Monday to Friday

Access guides

Accessibility information to support you.

Accessibility information about the Radiotherapy Village

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Accessibility information about the Radiotherapy Village 2 (R2)

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