Stereotactic ablative radiotherapy (SABR)
Stereotactic ablative radiotherapy (SABR) is a specialised type of radiotherapy. It is sometimes called stereotactic body radiotherapy. This information describes what SABR is, how and when it’s given, how it works, and some of the possible side effects.
This information should ideally be read with our general information about radiotherapy. We have separate information about stereotactic radiotherapy to treat brain tumours.
We hope this information will answer any questions you may have. If you have further questions you can ask your doctor or nurse at the hospital where you’re having your treatment.
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. We have more information about what you can do if a treatment isn't available.
Radiotherapy uses invisible, high-energy x-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.
What is stereotactic ablative radiotherapy (SABR)?
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This treatment uses scans and specialist equipment to precisely target radiotherapy to treat certain cancers accurately. It’s only suitable for some people, usually those with smaller cancers. SABR is usually given over a shorter time than standard radiotherapy.
SABR is known by a number of different names and this can be confusing. The names may relate to the area of the body being treated, the type of machinery being used or the length of treatment. The names include:
stereotactic body radiotherapy (SBRT)
stereotactic radiosurgery (SRS)
stereotactic radiation therapy (SRT)
The most commonly used brand names are CyberKnife™, Varian® and Elekta®.
We use the term stereotactic ablative radiotherapy throughout this section, or SABR for short.
Radiotherapy treatment works by damaging the DNA (our genetic material) in cancer cells. The aim is to stop the cancer cells growing and to shrink the tumour or completely destroy it.
Standard radiotherapy is delivered using equipment similar to a large x-ray machine, called a linear accelerator (linac). It delivers beams of radiation to the targeted area. This type of radiotherapy is usually given in a low, daily dose over a period of weeks.
SABR 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. SABR can be given with fewer treatments than standard radiotherapy. Between 3-8 treatments are normally given.
There are different machines that can be used to give SABR. Your radiographer will tell you which machine will be used for your treatment. The linear accelerator (linac) that delivers standard radiotherapy can be used to give SABR. There are also specially designed linacs for SABR, which are known by their brand name, such as CyberKnife™.
The machines work in different ways, so how you prepare and have your treatment will vary. The position you're in during treatment is important and will be carefully planned.
SABR can be used to treat small primary lung cancers (cancer that starts in the lung). It can also be used to treat secondary cancers (cancer that started in another part of the body) in the lung, liver, lymph nodes, spine and other sites. It is also being used to treat prostate cancer in a clinical trial.
SABR may be an alternative to surgery for people who can’t have surgery or where the tumour is in a difficult area to operate on. It is not suitable for everyone. Your doctor can talk to you about whether it’s a treatment option for you.
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
medical physicists - scientists who are involved in planning how the treatment is given
therapy radiographers - who are specially trained to operate the machines that give SABR
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 SABR treatment
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Planning your treatment is an important part of SABR, and you may need to visit various departments before having the treatment.
You may be asked to have fiducial markers placed in or near your tumour. These are very small and made of metal. They can be seen by the radiographer on x-rays and ensure your treatment will be delivered accurately. Your doctors will explain to you how this is done.
You may need a mould or cast made of the part of the body being treated. This is sometimes called an immobilisation device. This is to help you stay still and in the correct position during your treatment. Your doctors will tell you more about this if you need one.
Imaging and planning
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. Your radiographers will tell you how long these scans will take before they start.
A computer is used to plan your treatment, using the information from the scans. This ensures that the radiotherapy is precisely targeted at the tumour. The planning stage of SABR is very important.
Having your SABR treatment
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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 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 whether 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 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.
X-rays or images can also be taken during SABR treatment. This allows for adjustments to be made during each treatment due to tiny changes in the location of the tumour. For example, if the tumour moves slightly as you breathe in and out, the computer can adjust how the treatment is given.
You can usually go home when the treatment is finished.
Possible side effects of SABR
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Side effects can be mild or more troublesome, depending on the amount of radiotherapy given, which part of the body is treated and the length of the treatment. We have information here about the more common general side effects.
SABR 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 SABR and are usually temporary. Your healthcare team will explain any possible side effects to you before your treatment. It is important to tell your medical team about any side effects you experience.
Early side effects
These symptoms may appear just after your treatment and go away within weeks.
Tiredness – you may feel tired for a few weeks after the radiotherapy has been completed.
Skin reactions – your skin may become red, dry or itchy about 10-12 days after treatment.
Soreness and swelling in the treatment area.
Depending on the area being treated, these side effects may include:
chest pain, shortness of breath, raised temperature and eating/digestion problems in people being treated for a lung tumour
urine and bladder changes in people being treated for a prostate tumour
headaches in people being treated for a tumour in the spine
nausea, vomiting and pain in people being treated for a liver tumour.
Late side effects
Late side effects are thought to be rare but if they do occur, it’s usually months or years after treatment. Your doctor or specialist nurse can discuss all possible side effects in more detail with you.
SABR does not make you radioactive, and it’s perfectly safe for you to be with other people, including children, during and after your treatment.
Most people that have SABR can continue all their normal activities within 1-2 days.
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 treatments.
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.
This section has been compiled using information from a number of reliable sources, including:
Stereotactic body radiation therapy rationale and clinical experience. UpToDate. 2012. (accessed 13 December 2012).
Stereotactic radiosurgery and stereotactic body radiotherapy. RadiologyInfo. 2012.
With thanks to: Angela Baker, Research and Development Radiographer; Sarah James, Professional Officer, Society of Radiographers; Dr Peter Kirkbride, Medical Director; Stuart McCaighy, Clinical and Technical Development Radiographer; Dr Michael Williams, Consultant Clinical Oncologist; and the people affected by cancer who reviewed this edition.
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