What is stereotactic ablative radiotherapy (SABR)?

SABR is a type of external radiotherapy. It is sometimes called stereotactic body radiotherapy (SBRT). In this information we use the term stereotactic ablative radiotherapy, or SABR for short.

SABR may also have other names. What it is called is based on the:

  • area of the body being treated
  • type of machinery being used
  • length of treatment.

Stereotactic radiotherapy can also be used to treat brain tumours. This is sometimes called stereotactic radiosurgery (SRS). We have separate information about radiotherapy for brain tumours.

SABR is not available in all hospitals in the UK. Your doctor may refer you to a specialist hospital if they think it is a suitable treatment for you.

When is SABR used?

SABR may be used to treat:

  • a cancer that started in the lung (primary lung cancer) that is small in size
  • a cancer that has spread to another part of the body, such as the lung, liver, lymph nodes or spine – your doctor will give you more information about this
  • a type of cancer that started in the liver called hepatocellular carcinoma
  • some prostate cancers
  • some pancreatic cancers – this may be as part of a clinical trial
  • certain types of cancer when you cannot have surgery.

It may be used to re-treat areas of the body that have already been treated with radiotherapy. Sometimes if you have already had radiotherapy it is not safe to have it to the same area again. SABR is so precise it means you may be able to have it to an area already treated with radiotherapy.

SABR is not suitable for everyone. Whether it is suitable for you depends on:

  • where in the body the cancer is
  • the size of the cancer
  • whether the cancer has spread to other parts of the body from where it started.

Your doctor can talk to you about whether it is a treatment option for you.

How does SABR work?

Radiotherapy uses high-energy rays called radiation, to treat cancer. It destroys cancer cells in the area where the radiotherapy is given. The aim is to:

  • stop the cancer cells growing
  • shrink the tumour or completely destroy it.

Standard external beam radiotherapy delivers several beams of radiation to the treatment area. It is usually given as a number of daily doses over a period of weeks.

SABR uses many smaller, focused beams of radiation. The beams are directed from different angles that meet at the tumour. This means that the tumour gets a high dose of radiation, while surrounding healthy tissues get a much lower dose. This lowers the risk of damage to normal cells.

Treatment is usually spread over a few days and may take up to 2 weeks. Your doctor or radiographer will explain how many sessions you need and over how many days.

Different machines can be used to give SABR. Your radiographer will tell you which machine they will use for your treatment.

Planning SABR treatment

Planning your treatment is an important part of SABR. You may need to visit different departments in the hospital before starting your treatment.

It is important to tell the hospital staff about any medications and allergies you have. If you take painkillers, they may advise you to take them before your planning and treatment. This can make you more comfortable.

Moulds and radiotherapy masks

You may need to have a mould or radiotherapy mask made before radiotherapy planning starts. This is to help you stay still and in the correct position during your treatment. The radiographer may use moulds to keep a leg, an arm or other body part still during planning and treatment. Radiotherapy masks may be used for people having radiotherapy to the brain, head or neck.

Your doctor or radiographer will tell you more about this if you need one.

Imaging and planning

You usually start planning by having a CT scan. This takes a series of pictures of the area to be treated. The CT is taken when you are in the position you need to be in for treatment. You may also have an MRI scan or a PET scan.

The scans take pictures from different angles to build up a detailed picture of the area to be treated. Using the information from the scans, your doctor looks to see where you will need treatment. A computer is used to make an individual plan for your treatment. This ensures that the radiotherapy:

  • is precisely targeted at the tumour
  • has a lower risk of causing side effects.

You may have to wait several weeks before the plan is ready and you can start treatment. Your treatment team will let you know how long you can expect to wait. We have more information about your radiotherapy team.

It is important that the area being treated does not move too much during your treatment. Reducing movement allows your radiographer to direct the radiotherapy more accurately. They may show you some breathing techniques, or use gentle compression on your tummy area, depending on where you are having treatment. This is done during both planning and treatment.

Metal markers

You may have small metal markers placed in or near your tumour. They are sometimes called fiducial markers. The markers help find the exact location of the tumour to make sure the treatment is given accurately.

The markers are about the size of a grain of rice. They are put in using a needle during a CT or ultrasound scan. The doctor gives you a local anaesthetic injection to numb the skin. They may also give you a mild sedative. This will make you feel sleepy.

The doctor then makes a small cut and puts a needle through the skin over the tumour. When the tip of the needle is in the right place, they release the marker. Usually 2 or 3 markers are needed. The markers stay in your body permanently. They are very small so you will not be aware that they are there. It is safe to have scans.

Skin markings

You may have markings made on your skin. These help the radiographers position you for treatment.

Usually, tiny permanent markings are made in the same way as a tattoo. The marks are the size of a pinpoint. It can be a little uncomfortable while they are being made. But it makes sure that the treatment is directed accurately. If you have a mould or radiotherapy mask, the marks may be made on this.

These marks will only be made with your permission. If you are worried about them or already have a tattoo in the treatment area, tell your radiographer. They can discuss this with you.

Having SABR treatment

Before the treatment

The treatment room will be similar to the one where you had your planning scans. The radiographers position you carefully on the treatment couch and adjust its height and position. They use the marks on your skin (or on your radiotherapy mask, if you have one) to help get you in the same position you were in for your planning scan.

It is important that you are comfortable, as you have to lie as still as possible during the treatment. Tell the radiographers if you are not comfortable.

Having the treatment

When you are in the correct position, the radiographers leave the room and you start your treatment. There is a camera so they can see you from outside the room. There is usually an intercom, so you can talk to them if you need to during your treatment.

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

You may have all the treatment at once, or it might be broken up with short breaks. Treatment time can vary, depending on the type of machine and type of cancer being treated. Your radiographer will tell you how long your treatment will take.

The way SABR is given is different depending on which machine they use. Usually, part of the machine moves around you and gives the radiation dose from different angles. Sometimes the treatment couch you are on also moves.

The radiotherapy machine may take x-rays and scans during SABR treatment. The pictures show if adjustments need to be made during each treatment. For example, if the tumour moves slightly as you breathe in and out, the computer can adjust how the treatment is given. This makes sure that the treatment is always given to the correct area.

You can usually go home when the treatment is finished. SABR does not make you radioactive. It is safe for you to be with other people, including children, during and after your treatment.

Possible side effects of SABR

You may have some side effects during or after SABR. But this treatment usually causes fewer side effects than standard external beam radiotherapy. This is because the healthy tissue gets a lower dose of radiation.

Side effects do not usually happen straight away. They may develop during your course of treatment or in the days or weeks after treatment finishes. Sometimes side effects get worse for a time after you have finished radiotherapy before they get better. There may also be a small risk of side effects that are long-term. Or effects that start months or years after radiotherapy. These are called late effects. Your doctor, specialist nurse or radiographer will talk to you about any late side effects you may develop.

It is difficult to know exactly how you will react to treatment. Your team will explain what to expect. Always tell them if you have side effects during or after radiotherapy. They can give advice and support to help you cope.

General side effects

The general side effects of SABR include:

  • feeling tired for a few weeks after you finish treatment
  • skin reactions in the treatment area, such as red, dry, itchy skin, or darkening of the skin, about 10 to 12 days after treatment
  • soreness and swelling in the treatment area.

Specific side effects

Some side effects depend on the area being treated. For example, you may have:

  • chest pain
  • a cough
  • shortness of breath
  • a raised temperature
  • eating or digestion problems.
  • Liver or pancreatic tumours

    If you are having SABR for a liver tumour or pancreatic tumour, you may:

  • Prostate cancer

    If you are having SABR for prostate cancer, you may have urinary problems such as::

    • needing to pass urine (pee) more often
    • blood in your urine
    • discomfort when you pass urine.

Follow-up after treatment

After you finish treatment, your doctor, specialist nurse or radiographer will arrange a follow-up appointment. This is usually 4 to 8 weeks after your treatment ends. We have more information about lifestyle and well-being after cancer treatment.

Getting support

Macmillan is here to support you. If you would like to talk, you can do the following:

About our information

  • Reviewers

    This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer. It has been approved by Senior Medical Editor, Dr David Gilligan, Consultant Clinical Oncologist.

    Our cancer information has been awarded the PIF TICK. Created by the Patient Information Forum, this quality mark shows we meet PIF’s 10 criteria for trustworthy health information.

Date reviewed

Reviewed: 01 August 2022
Next review: 01 August 2025
Trusted Information Creator - Patient Information Forum
Trusted Information Creator - Patient Information Forum

Our cancer information meets the PIF TICK quality mark.

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