Stereotactic radiotherapy (SRT) for brain tumours

Stereotactic radiotherapy (SRT) is a specialised type of radiotherapy that can be used to treat small brain tumours, recurrent gliomas and secondary brain tumours (cancers that started elsewhere but have spread to the brain). It’s only suitable for some people and isn’t yet widely available in the UK.

SRT uses scans and specialist equipment to direct thin beams of radiation very precisely at the tumour. The tumour receives a high dose of radiation, while surrounding healthy tissue receives a low dose.

You will have a CT (computerised tomography) scan to carefully plan the treatment. You may have other scans to improve the accuracy. You may need a specially made mask and/or a head frame to help you stay in the correct position during treatment.

To deliver SRT, radiographers will fix your mask and head frame in position. The radiographers won’t be in the same room with you during treatment, but will be able to speak with you (usually through an intercom) and guide you through the process.

SRT usually causes fewer side effects than standard radiotherapy. These may include temporary swelling of the area being treated, soreness, tiredness, itchy skin and hair loss. Your healthcare team can give you advice on ways of coping with these side effects. SRT does not make you radioactive.

What is stereotactic radiotherapy (SRT)?

Stereotactic radiotherapy (SRT) is a specialised type of radiotherapy that can be used to treat different parts of the body. This information is about how it’s used to treat brain tumours. It describes what SRT is, how and when it’s given, how it works, and some of the possible side effects. It should ideally be read with our general information about radiotherapy.

This treatment is currently not widely available in the UK. You may be referred to a specialist hospital if your doctor thinks it’s a suitable treatment for you.

Radiotherapy uses invisible, high-energy rays to treat cancer. It works by destroying cancer cells in the area being treated. Although normal cells can also be damaged by radiotherapy, they can usually repair themselves.

SRT uses scans and specialist equipment to aim radiotherapy very precisely and accurately at certain types of brain tumours. It’s only suitable for some people. SRT is usually given over a shorter period of time than standard radiotherapy.

SRT is known by a number of different names and this can be confusing. These include:

  • stereotactic radiosurgery (SRS)
  • stereotactic brain radiosurgery
  • stereotactic radiation therapy (SRT)
  • Gamma Knife (a machine used to administer SRT)
  • CyberKnife (a machine used to administer SRT).

We use the term stereotactic radiotherapy, or SRT for short.

When is SRT used?

SRT can be used to treat small brain tumours, recurrent gliomas (a type of brain tumour) and secondary brain tumours (metastases – where a cancer has spread to the brain from another part of the body). It is also sometimes used for some benign (non-cancerous) brain tumours. It’s not suitable for everyone with brain tumours. Your clinical oncologist can discuss whether it may be appropriate for you.

How does SRT work?

Radiotherapy treatment works by damaging the DNA in cancer cells. DNA is what makes up our genes, which control how our cells grow and work. The aim of radiotherapy treatment is to stop the cancer cells growing and to shrink the tumour or completely destroy it.

Standard radiotherapy is delivered using a piece of equipment called a linear accelerator (linac), which is similar to a large x-ray machine. It delivers many beams of radiation to the targeted area. This type of radiotherapy is usually given in low, daily, doses over a period of weeks.

SRT uses many smaller, thin beams of radiation directed from different angles that meet at the tumour. The tumour itself receives a high dose of radiation, while the individual beams that travel through the surrounding healthy tissues are of a low dose. This lowers the risk of damage to normal cells. Unlike standard radiotherapy, SRT can be given as a single treatment (when it’s called stereotactic radiosurgery) or between 2–8 treatments. SRT can also be given over 5–6 weeks if required – in a similar way to standard radiotherapy.

There are different machines that can give SRT:

  • The Gamma Knife system only treats brain tumours.
  • Linear accelerator (linac) machines that deliver standard radiotherapy can be used to deliver SRT. There are also linear accelerators that are specially designed to give SRT. These are known by their brand names, such as CyberKnife.

The machines work in different ways, so how you prepare for and have your treatment will vary. The position you’re in while having treatment is important and will be carefully planned.

Radiotherapy staff

There are various members of staff you may meet during the planning and delivery of your treatment. They include:

  • a clinical oncologist – a doctor trained in the use of radiotherapy and chemotherapy
  • a neurosurgeon – a doctor who specialises in brain surgery
  • medical physicists – scientists who are involved in planning how the treatment is given
  • therapeutic radiographers – who are specially trained to operate the machines that give SRT
  • a mould room technician – who makes masks or moulds for people who need to keep their head still during treatment (see below)
  • nurse and radiographer specialists – who give information and support during your treatment.

Planning your SRT treatment

Planning your treatment is an important part of SRT and you may need to visit various departments before having the treatment.

Moulds and head frame

You may need a mask (mould) and/or a head frame to help you stay still and in the correct position during treatment. If you have any facial hair, you may be asked to shave it off before your mask is made.

A mould can be made in one of two ways:

  • A thermoplastic mask is made of a sheet of plastic mesh that’s softened in warm water, placed over your head, and shaped to form a close-fitting mask. This takes about five minutes to set. Holes will then be made for your eyes, nose and mouth. This is the method that’s usually used.
  • A clear perspex mask is made from a plaster cast of your face. The plaster cast is made using strips of wet plaster bandage laid across your face. The plaster takes about five minutes to set. This method is less commonly used.

It’ll take about an hour to have your mask made and you’ll be able to go home afterwards.

If you’re having SRT using a Gamma Knife machine, a metal head frame will be made before the planning stage begins. The head frame will be attached to the couch you lie on and either to your mask or your head. The head frame is fitted on the same day that you have SRT. A neurosurgeon will attach the frame to four points of the skull using local anaesthetic. While this sounds scary, it may be a bit uncomfortable but shouldn’t be painful. The frame directs the radiation beams accurately and helps to keep you still during treatment.

If you’re treated on a linear accelerator, you’ll only need to wear a thermoplastic mask. Sometimes you may need a different frame that uses mouth bites and head supports that are specially made for you.

We have more information about how radiotherapy masks are made.


The next stage of planning is to have a CT (computerised tomography) scan – sometimes called a CT simulator. This takes a series of pictures of the area to be treated. You may also have other scans such as an MRI (magnetic resonance imaging) scan to improve the accuracy of your treatment. These scans provide images from different angles to build up a three-dimensional picture of the tumour. You’ll wear your mask during the scan to help position you correctly. Your radiographer will tell you how long the scans will take before they start.

A computer is used to plan your treatment. This ensures that the radiotherapy is precisely targeted at the tumour.

Having your SRT treatment

It’s important to tell the hospital staff about any medications and allergies you have. You may be asked not to eat or drink for a few hours before the treatment. If you take painkillers, you may be advised to take them before your treatment so that you’re comfortable.

The treatment room will be similar to the one you had your planning in.

The radiographers will position you ready for your treatment. They will fix your mask and head frame in position as needed. If you’re having SRT with Gamma Knife, the mask and head frame are used to help position you correctly. If you’re having SRT using CyberKnife™, you may only need a mask.

The radiographers won’t be in the same room with you when you’re having the treatment, but they will guide you through the process. Once you’re in the correct position, they will leave the room and you’ll be given your treatment.

You will be able to communicate with them while having treatment. There may be a camera or window in the room so the radiographers can see you. Many treatment rooms also have an intercom so the radiographers can talk to you while you have your treatment. If you have any problems, you can raise your hand or speak to them through the intercom and they will come in to help you. Treatment rooms can vary in some hospitals, and the radiographer will tell you the best way to communicate with them during treatment.

The radiographers will take care to protect your privacy so that nobody else can see you.

The treatment itself is painless. You may hear a slight buzzing noise from the radiotherapy machine during treatment. Some treatment rooms have CD or MP3 players so you can listen to music to help you relax. If you’d like to listen to your own music, ask your radiographer if this is possible.

Treatment may be given in one go or it might be broken up with short breaks. Treatment time can vary from about 15 minutes to four hours, depending on the type of machine. Your radiographer will tell you how long your treatment will take.

Linac machines are similar to Gamma Knife machines but have a part called the gantry that moves around you to give the radiation dose from different angles. The bed you’re positioned on may also be able to move. CyberKnife machinery has a robotic arm that moves around you, delivering the dose of radiation from different angles.

You can usually go home when the treatment is finished.

Possible side-effects of SRT

Side effects can be mild or more troublesome depending on the amount of radiotherapy given and the length of your treatment. SRT usually causes fewer side effects than standard radiotherapy as the healthy tissue is exposed to a lower dose of radiation.

The side effects described here won’t affect everyone who has SRT to treat a brain tumour. Side effects are usually temporary. Your healthcare team will explain any possible side effects to you before your treatment. It’s important to tell your medical team about any side effects you experience.

  • Seizures – this is rare, but sometimes after SRT there is a slight risk of a seizure. It’s more common in people who have had seizures before the treatment. Let your doctor know if this happens.
  • Temporary swelling of the area that is being treatedsteroids are often prescribed before and after the treatment session to help reduce this.
  • Soreness – for a few hours after treatment, there may be some discomfort in the areas where the head frame was fixed to the skull.
  • Headaches – these can be controlled with painkillers, or sometimes steroids will be prescribed by your doctor.
  • Tiredness – this may last a day or two. Allow yourself plenty of rest.
  • Feeling sick (mild nausea) – occasionally, some people feel sick but this can usually be treated effectively with anti-sickness drugs (anti-emetics).
  • Dizziness.
  • Vertigo – a sensation that you, or your environment, is moving, which can affect your balance.
  • Itchy skin – this may last for a week or two but will ease. The radiographers looking after you will be able to advise you about skin care.
  • Hair loss – you will lose your hair in the treatment area. Most hair loss is temporary but, unfortunately, it may be permanent for some people. This will depend on the dose of treatment you have had. Sometimes, hair grows back with a slightly different colour and texture, or perhaps not as thickly as before. It usually starts to grow back within 2–3 months of finishing treatment.

SRT does not make you radioactive, and it’s perfectly safe for you to be with other people, including children, during and after your treatment.

After SRT treatment

Some people find their brain tumour symptoms temporarily get worse after the treatment has finished. This can make them think their tumour is getting worse. But it may be a reaction to the radiotherapy treatment or because the steroid treatment has been reduced or stopped. Let your doctor know if you’re worried about continuing symptoms.

Your feelings

You may experience many emotions, including anxiety and fear. These are normal reactions and are part of the process many people go through in trying to come to terms with their condition and its treatment.

Everybody has their own way of coping with difficult situations. Some people find it helps to talk to family or friends, while others prefer to seek help from people outside their situation. Some people prefer to keep their feelings to themselves. There is no right or wrong way to cope, but help is available if you need it. Our cancer support specialists can give you information about counselling in your area.

Back to Radiotherapy explained

Who might I meet?

You will meet many different specialists before, during and after radiotherapy treatment.