Stereotactic radiotherapy

'Stereotactic radiotherapy' means the use of computers and scanners to produce 3D images that very accurately locate a tumour within the brain and direct radiotherapy treatment towards it.

Many small beams of radiation are directed from different angles around the head towards the tumour. Where these beams meet and overlap at the site of the tumour, the doses of radiation add together and create a highly focussed, high dose of radiation to destroy the tumour cells.

To achieve this, it is extremely important to position the head in exactly the same place each time and keep it very still.

What is the difference between SRT and conventional radiotherapy?

Though some types of conventional radiotherapy deliver radiotherapy beams from various angles around the head and work in a similar way to SRT, the difference with SRT is that it uses computers to pinpoint the tumour even more accurately. It is also stricter in keeping your head still during treatment.

As a result, a smaller area outside the tumour needs to be given radiotherapy to make sure the correct dose is given to the whole of the tumour. This means fewer healthy cells receive a high dose of radiation and people generally experience fewer side-effects.

The greater accuracy also means a higher dose can be safely given to the tumour, or fewer treatment sessions may be needed.

Often only one high dose of treatment is needed. This is called stereotactic radiosurgery (SRS). (Treatment given over several sessions is called fractionated stereotactic radiotherapy or FRST).

Can I have SRT/SRS?

SRT/SRS are generally only used for small tumours (less than 3cm at the widest part) to ensure the same high dose of radiation can be given across the whole tumour.

Brain tumours that SRT/SRS are suitable for include:

  • Small low grade tumours with an obvious edge
  • Small gliomas that have come back (low and high grade)
  • Haemangioblastomas that couldn't be completely removed or which came back after surgery
  • Other small low grade tumours, such as:
    • Vestibular schwannomas (acoustic neuromas)
    • Meningiomas at the base of the skull
    • Pituitary adenomas
    • Chordoma
  • Secondary brain tumours (metastases)

SRT/SRS may NOT be suitable if the treatment area includes important nerves which could become damaged.

It is important to appreciate that SRT/SRS is not suitable for everyone.

Additionally, not all hospitals have the specialised equipment and staff required.

Your oncologist can talk to you about SRT/SRS and whether it is suitable for you.

What does having SRT/SRS involve?

Much of the SRT/SRS procedure is similar to conventional radiotherapy and it uses the same type of radiation i.e. X-rays.


The positioning of your head in the same place is extremely important, particularly if you are having treatment over several sessions (fractionated SRT), to make sure that the beams are accurately hitting the same target each time.

There are two main ways of achieving this targeting:

Stereotactic mask
This is similar to the mask used in conventional radiotherapy, but it is closer fitting to ensure your head remains still.

Making the stereotactic mask can take up to 45 minutes.

You only have to wear it when you go for treatment or have a planning scan.

Head frame
This is more often used for SRS.

A frame is made to fit your head and attached, through your skin, to the surface of your skull, using four small pins. You will be given local anaesthetic at these points.

You may feel some tightness or pressure, and these areas may be sore afterwards. Wearing the frame can be quite tiring.


Scans will be taken with, and without, the mask or frame on, to allow your specialists to create a 3D image of your tumour, plan your treatment and set up the machine to target your tumour precisely.

This planning stage can take several hours.

Once planning is completed, you will receive your treatment.

The procedure

As with conventional radiotherapy, you will wear your mask (or head frame) and be positioned on a treatment table. The medical staff will leave the room, but will be able to see and hear you, and you can hear them. You may be able to listen to music during treatment to help you relax.

The treatment is usually given by a machine similar to a large X-ray machine, which has an attachment that moves round your head delivering small beams of radiation from different angles. This does not hurt.

The length of the treatment session varies depending on the:

  • Size of your tumour
  • Dose of radiotherapy needed
  • Machine used
    • LINAC machine (20 – 40 minutes)
    • CyberKnife® (30 – 90 minutes)
    • GammaKnife® - used for SRS (up to 4 hours)

No machine involves an actual knife and there is currently no identified advantage of one machine over another.

You will be at the hospital longer than these times, to allow for fitting the mask and positioning you correctly.

After treatment, your mask or head frame will be removed and you can usually go home – straightaway for FSRT, or after some monitoring, which may be overnight, for SRS. It is advisable to arrange transport, as you may feel very tired.

Typically, a course of FSRT is 5 -25 daily treatment sessions, but it will be tailored to your individual needs.

Before treatment begins (or shortly afterwards) your doctor may also give you steroids to reduce brain swelling. With SRS, you may also have anti-seizure drugs to help prevent a seizure (fit).

After treatment

FSRT and SRS generally have fewer side-effects than conventional radiotherapy, but you may experience some. Most are short-lived.

Common short-term side-effects

  • Feeling tired for a few days - make sure you rest
  • Dull headache (if you had a head frame) – can be eased with painkillers
  • Tender, bleeding or itchy pin sites (if you had a head frame) - your health team will give information about keeping these clean to reduce the risk of infection

Rarer short-term side-effects

  • Feeling sick, dizzy or faint - steroids given before or immediately after treatment help prevent this
  • Hair loss – occasionally if your tumour is near to the surface of your skull
  • Seizure (fit) - after radiosurgery (SRS)

You are not allowed to drive for at least one month after SRS treatment, in case you have a seizure, even if you have not had seizures previously. (For more information, please see our Driving and brain tumours webpage.)

It is important to be aware that radiotherapy (of any type) can cause swelling in the tissue around the treated area. This can make it look like the tumour is growing again on a post-treatment MRI scan. This is called 'pseudo-progression' and can make it difficult to assess how effective the treatment has been.

Long-term side-effects

  • Radiation necrosis

Some people can develop an area of dead cells in the treated region. This generally happens six months to two years after SRT/SRS, but can up to decades after treatment. It is more likely if you also had chemotherapy.

Often there will be no symptoms, as the affected area is very small. If symptoms do occur, usually due to swelling, steroids can be given to treat this. Occasionally, surgery may be required to remove the dead tissue.

If you experience or are concerned about any side-effects, speak to your doctor.

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