What is Gamma Knife radiosurgery?
Gamma Knife radiosurgery is an established stereotactic radiosurgery (SRS) technique which is able to deliver large doses of highly precise radiation to treat tumours, vascular malformations and other abnormalities of the brain. Despite its name, this treatment does not involve a knife or surgery. It is often used to treat both benign (non-cancerous) brain conditions and metastatic (secondary) cancer deposits in the brain.
At the GenesisCare Centre for Radiotherapy at Cromwell Hospital in London, SRS treatment is delivered using a Gamma Knife® Icon™ machine – an advanced technology using a precise beam of radiation to treat brain tumours. The Gamma Knife uses up to 192 tiny beams of gamma radiation to target the area with sub-millimetre accuracy. This treatment is delivered either in a single session or within a few sessions depending on the condition being treated.
With the Gamma Knife radiosurgery, we are able to minimise the radiation to the surrounding healthy brain tissue and thereby reduce the risk of damage to it.
Benefits of Gamma Knife radiosurgery
One of the major benefits of Gamma Knife radiosurgery compared to open surgery is that it is non-invasive. As a result, it usually has minimal complications
Goes further to treat you
Gamma Knife enables us to treat hard-to-reach brain tumours that conventional surgery cannot
Does not leave a mark
Unlike open surgery, you won’t have scars or need to shave your head prior to Gamma Knife treatment and it’s unlikely that you’ll experience any significant hair loss either
Many Gamma Knife patients can be treated as a day case procedure. You should be able to return to most of your normal activities in 1-2 days compared to 2-6 weeks with open surgery
Limits risks and side effects
You avoid risks such as infection or bleeding that are associated with open surgery. Meanwhile, side effects such as headache and nausea are very rare and temporary
Is Gamma Knife radiosurgery right for you?
We use Gamma Knife radiosurgery to treat a variety of brain conditions, from benign brain conditions to brain metastases (secondary brain tumours). Your consultant will work with a team of consultant neuro-surgeons, neuro-oncologists and neuro-radiologists, as well as other healthcare professionals, to decide if Gamma Knife radiosurgery is the best treatment option for you after careful evaluation of your condition.
Gamma Knife for benign brain conditions
Gamma Knife radiosurgery is a non-surgical radiation therapy and a well-established SRS technique that delivers large doses of highly targeted radiation to treat tumours and benign conditions including:
- Vestibular schwannoma
- Pituitary adenoma
- Other skull base tumours
- Arteriovenous malformation
- Trigeminal neuralgia
- Some forms of epilepsy, Parkinson’s disease and tremors
Gamma Knife for metastatic brain tumours
Gamma Knife radiosurgery has significant benefits over conventional whole-brain radiotherapy for metastatic brain tumours, also known as secondary cancer or stage 4 cancer. By limiting radiation to the surrounding healthy brain tissue, we can reduce immediate and late side-effects and hence offer a better quality of life.
However, SRS may not be suitable if:
- The treatment area includes certain important nerves that could be accidentally damaged by radiation
- Volume of disease is more than 20cc (roughly this would translate to individual tumour size <3-4cm)
- If you have uncontrollable disease outside brain
Your Gamma Knife treatment
Here’s what to expect on the day of your Gamma Knife radiosurgery, it’ll involve fitting you with a face mask or head frame, planning and treatment. You’ll be asked to wash your hair before arriving and not to eat or drink anything for four hours, unless you have diabetes.
You’ll be fitted with a head frame or face mask to help improve the accuracy of your Gamma Knife radiosurgery and keep your head still during treatment. Your doctor will let you know before your appointment which you require. The frame will be fitted on the same day as your treatment. If face masks are to be used this can be done a few days before or on the day before your treatment.
Head frame fitting
Your consultant will inject local anaesthetic into four places on your head. Once the areas are numb, they’ll attach the frame to your head with four screws. It takes around 15 minutes to fit and you’ll keep it on until your Gamma Knife treatment has finished. You may feel discomfort but once the frame is fitted this will disappear in a few minutes. You may also feel some discomfort where the frame was attached to your head after your treatment has finished and the local anaesthetic has worn off.
Face mask fitting
A sheet of plastic that has been softened in an oven will be placed over your face and head and moulded to fit you. It’ll remain on your face as it hardens, but you’ll be able to breathe normally and shouldn’t feel any discomfort. The mask will be removed once it’s dried.
Ahead of Gamma Knife radiosurgery, you’ll need an MRI scan – this helps us accurately direct the radiation beam during treatment and set the optimum dose according to your tumour’s position, size and shape.
Before your MRI, you’ll be injected with a special dye called a contrast agent, which helps show certain structures more clearly on the scan.
If you’re wearing a head frame for your treatment, you’ll also be required to wear it for your MRI scan. You’ll have to lie in a still position for the duration of your scan, around 45 minutes, during which your radiographer will be able to speak to you via an intercom.
Your care team, including your consultant, will then use the information from the scans to plan your Gamma Knife treatment. This can take from 30 minutes to a few hours. While you’re waiting, you’ll be given something light to eat and drink, and you can watch TV, read or chat with a friend or relative. You will keep your head frame on during this time if you have one.
After your planning appointment, your radiographers will take you to the Gamma Knife treatment room. You’ll be helped into position on the treatment couch and your head will be held in place with your head frame or face mask again. If you’re wearing a face mask, a marker will be placed on the tip of your nose once the mask is in place. Your radiographer will confirm you’re set up correctly for treatment.
When you’re ready, your radiographers will leave the room, but you’ll still be able to talk to them throughout the treatment via an intercom. The bed will move inside the Gamma Knife machine through an open door and treatment will begin. If you have metastatic cancer and are having more than one metastasis treated, the bed will automatically move you into position between each target site.
You won’t be able to feel the Gamma Knife treatment and it may take anywhere between 30 minutes and four hours, depending on the size and location of your tumour.
When the Gamma Knife treatment has finished, your radiographer will come back into the room and help you off the couch. If you have a head frame, it’ll be removed and you’ll be able to go back to your room to rest.
You may feel sick or have a headache for a few hours after your treatment. If you’re feeling unwell or your appointment was later in the day, you may be asked to stay overnight, but you should be back to your normal activities the next day. In some instances, patients can have fractionated treatments which may be three or five sessions over several days, this will discussed with you at your consultation if necessary.
Your doctor will let you know what your follow-up schedule will be, depending on the number, size, location and prognosis of your tumours.
Usually, a member of your care team will call you to check on your recovery around a week after your Gamma Knife treatment. Depending on your diagnosis, you’ll then have a review two to three months later (metastatic cancer) or six months later (benign tumour) with your consultant and a follow-up MRI of your brain to see how the treatment has worked.
Gamma Knife side effects
All treatments carry the risk of some side effects, however, you can expect fewer side effects with stereotactic radiosurgery (SRS) than conventional radiotherapy because its greater accuracy means that the risk of damage to healthy brain tissue is lower.*
Not everyone experiences side effects but your risk may be affected by your general health, other treatments you’ve had and the location of your lesion or tumour.
If you do experience some changes after treatment, your care team will advise you on the best way to deal with them.
* Risk of seizures is slightly increased after treatment but usually only affects people who have a history of seizures. Ask your medical team for advice. If you have a seizure for the first time, go straight to your nearest hospital’s accident and emergency department.
These usually disappear within two to four weeks of treatment:
- Pin site pain
- Nausea and/or vomiting
- Seizures (fits)*
- Temporary worsening of your symptoms
- Allergic reaction to MRI contrast agent
Around 10% of people notice side effects months, or even years, after SRS. These are related to the treatment area within the brain and may include:
- Local hair loss
- Hearing loss
- Loss of brain function
- Memory loss
- Pituitary gland damage
- Radiation damage to the normal brain
- Visual impairment
- Secondary cancer years later, though this is rare
Up to half of these side effects can be successfully treated. It’s important that you attend your follow-up visits and scans so we can identify and treat any problems as soon as possible.
If you have a brain tumour, you may have to notify the DVLA. You may not be allowed to drive for a certain period of time depending on the type of tumour and treatment received. Your doctor can advise you further.