Stereotactic Radiation or radiotherapy (SRT) uses radiation from numerous angles around the body meaning that the tumour receives a full dose, but the different lines of attack cause a lower dose and less healthy tissue damage; here we look at two forms called Gamma knife and Cyberknife.
The Cyberknife uses high energy X-rays, the Gamma knife uses gamma rays; the Cyberknife moves around the brain or body to fixed points delivering radiation from those points; the Gamma Knife is more restricted to brain tumours using a fixed frame or mask. Both are tightly targeted on a tumour from multi-delivery points. Both use photon radiation. Here we provide more about both treatments.
The Gamma Knife
Introduced in 1968 by Dr Lars Leksell a Swedish Neurosurgeon, the Gamma Knife uses Cobalt as its radiation source. A mask is employed, and the radiation angles are determined from a 3D plan. In this way, multiple beams from different directions can pinpoint a tumour in the cranium - for example, a brain tumour. This aims to allow for a full radiation delivery at the target point with less damage before and after the target point, as might occur with single beam radiotherapy. This is Stereotactic Radiotherapy.
The Cyberknife
Dr John Adler of Stanford Medical School developed the Gama Knife concept into a machine with a moveable arm that allowed the 'gun' to fire from multiple predetermined points. This flexibilty meant that tumours not just in the brain, but anywhere in the body could be targeted.
To quote from the makers, the Accuray company: ’The CyberKnife Robotic Radiosurgery System is a non-invasive alternative to surgery for the treatment of both cancerous and non-cancerous tumors anywhere in the body, including the prostate, lung, brain, spine, liver, pancreas and kidney. The treatment, which delivers beams of high dose radiation to tumors with extreme accuracy, offers new hope to patients worldwide’.
So its not a knife; and it’s not really surgery!
To quote from Wikipedia: ’The CyberKnife is a frameless robotic radiosurgery system used for treating benign tumors, malignant tumors and other medical conditions. The system was invented by John R. Adler, a Stanford University Professor of Neurosurgery and Radiation Oncology, and Peter and Russell Schonberg of Schonberg Research Corporation. It is made by the Accuray company headquartered in Sunnyvale, California’.
The CyberKnife system is a method of delivering radiotherapy, with the intention of targeting treatment more accurately than standard radiotherapy. The two main elements of the CyberKnife are -
(1) The radiation produced from a small linear particle accelerator, and,
(2) A robotic arm which allows the energy to be directed at any part of the body from any direction.
In simple terms
CyberKnife can be used to treat virtually all tumours. It involves a number of X-ray machines (from a LINAC machine) around the body working together to see the tumour in real time (monitoring its movement, for example, as you breathe).
A synchronised robot can then deliver radiation not from one angle (as with standard radiotherapy), but from several or many. The idea being that each beam of radiotherapy is a far lower dose, so in theory there is less surrounding tissue damage. But since all the lesser beams are tightly focused on the tumour, it alone receives the full whammy. And much higher doses than normal may be delivered via an accelerator gun. Indeed, higher doses, and fewer sessions of treatment. With Cyberknife the high dose beams of radiation are termed Stereotactic Radiosurgery or SRS.
As you would expect, patients have CT scans and other investigate procedures in advance of treatment and usually a plastic mould is completed to hold the patient as still as possible during treatment. Treatment does not hurt at all.
The original idea was formulated in 1990; the CyberKnife has had FDA approval since August 1991.
Ten years on:
By 2010 there were only two CyberKnife machines in the UK - at The London Clinic and the Harley Street Clinic - and they cost 2million each. But now the NHS has machines, for example at London’s Mount Vernon Hospital and The Royal Marsden.
It is expensive: A series of sessions at a private clinic costs up to 20,000 pounds sterling. About the same cost as the genuinely far less invasive
Proton Beam Therapy (used widely in America but almost boycotted in the UK).
So just what does the CyberKnife do?
It is claimed that the accuracy of the system enables tumours to be treated that are in difficult positions, such as near the spinal cord.
Dr Bill Bice, chief medical physicist at The London Clinic, says: ’By focusing the radiation carefully, you maximise the dose to the tumour cells while minimising the amount received by the surrounding normal cells.
Normal cells are much better at repairing themselves between treatments than cancer cells. Although there is a risk of causing secondary cancers, this occurs infrequently and there is a long latent period, up to 20 years, before cancer develops.
The CyberKnife can deliver radiation with sub-millimetre precision, which helps to avoid side effects.
Most conventional radiotherapy is delivered with an uncertainty of between five millimetres and one centimetre.
Because of this, patients would have to be immobilised - for a brain tumour this meant screwing four pins into the patient’s scalp to mount a head frame for treatment, which was very uncomfortable.
The CyberKnife moves around the patient, so they can be immobilised in a far gentler fashion, with a mask that fits over the head.
As the machine records images throughout the treatment and moves with the patient’s breathing, if they move it can correct itself. Conventional radiotherapy involves 20 or more short sessions with low-dose radiation.
With the CyberKnife, a patient may need only three to five sessions.’ (Daily Mail)
An Alternative Cancer Therapy?
Ten years on and Dr Bice claims that the CyberKnife can treat cancers that were previously thought unsuitable for radiotherapy - including on the spine - which can’t be operated on because of the risk of paralysis - and even some lung cancers.
However, CyberKnife is a new technology and long-term research is non-existent really. So is research on side-effects. Whether it is better than traditional radiotherapy isn’t clear-cut.
Research in The Lancet suggested that the lower, muti-angled doses had reduced memory damage in treated brain tumour patients, but that a year after treatment only a third as many were still alive when compared with the group who had traditional whole-brain radiotherapy.
Concerns
1. The crucial issue is simple: ’Is this a triumph of marketing over reality’. Standard radiotherapy has been developing rapidly, but sounds boring and dangerous, whereas terms like ’Designer drugs’ and ’CyberKnife’ sound progressive and sexy. Radiotherapy experts bemoan the UK Government top-up drug fund while they still use outdated radiotherapy kit.
2. CyberKnife may seem trendy but there are no phase III clinical Trials, and little to suggest that it works better with less side-effects that the best of radiotherapy in British Hospitals. Yet people with cancer enquire all the time about this highly expensive treatment.
3. One of the claims is that because the cyberknife moves around the tumour the damage and side-effects affecting any piece of tissue is minimal. However, this is a claim, without rigorous evidence or clinical trials to support it. While CyberKnife treatment requires no anaesthesia and patients can usually be treated and go home on the same day, it is not without side-effects. For example, in colorectal cancer CyberKnife treatment can still cause severe ulceration and bleeding. Advocates claim that the threat is to a smaller area than standard radiotherapy.
4. Treatment is expensive and some regional NHS authorities will not send patients to Mount Vernon as they are not yet convinced the treatment works better than standard radiotherapy. Both Mount Vernon and Royal Marsden are trying to get data together; at the moment it is all very anecdotal with little more to support it than any other alternative cancer therapy. Even after 10 years.
Thus, trendy or not, with excited staff, Cyberknife remains in the Alternative treatment section of CANCERactive until we have a good volume of hard data.
The Gamma Knife, the Cyberknife, bottom line
The Gamma Knife is a little old fashioned in that is requires a mask before radiation is delivered into your brain from multiple points. The Cyberknife Radiosurgery system requires no mask and can deliver radiation from multiple locations to anywhere in the body.
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