A new high-precision radiosurgery technique which will allow doctors to control a third of all brain tumours - and avoid the brain damage caused by conventional treatment - has been developed by scientists and clinicians at The Institute of Cancer Research and The Royal Marsden hospital.
The technique - which is known as conformal stereotactic radiotherapy - delivers precision irradiation treatment with surgical accuracy. It combines the latest advances in shaped-beam radiotherapy and 3D scanning methods to enable doctors to reach tumours buried deep within the brain.
Localised benign tumours account for one-third of all cases of brain tumour and must be treated as they may grow and kill the patient if not controlled. Some may be cured by surgery but many cannot be removed as they lie deep in the brain. Although conventional radiotherapy is able to control up to 90 per cent of these cases, some patients suffer damage to the brain, leaving them cured of their tumours but with disability.
Now doctors are able to treat up to 100 per cent of these localised tumours with high-precision radiation - without the risk of life-changing side-effects. This is of particular importance when these tumours develop in children since conventional radiotherapy can damage the developing brain and lead to severe impairment.
Dr Michael Brada, who led teams at The Institute and The Royal Marsden in developing this treatment commented: "This is the first study in the UK to develop the technology and put the theory into practice - and we are very encouraged by the early results. We have developed this technique to be easily exportable to radiotherapy units in hospitals around the country and it is such a technical improvement that I am optimistic it will be taken up by other centres before the trials here are complete."
Although relatively rare, brain tumours are the most common solid tumour in children, and in adults they are second only to stroke as the leading cause of death from neurological disease. About one-third are localised tumours occurring deep in the brain and treatable only with radiotherapy - a treatment which can be administered much more safely and accurately using the new technique since, with standard radiotherapy methods, doctors are unable to avoid irradiating healthy brain tissue.
The first stage of the treatment process involves taking an accurate image of the patient's brain using a combination of Magnetic Resonance Imaging (MRI) and standard CT (CAT) scans. The dimensions of the tumour, healthy brain and very sensitive parts of the brain are then fed into sophisticated computers which interpret the information and create an individualised treatment plan. Since 95 per cent of brain tumours are not uniformly spherical, very precise dimensions for irradiation are needed.
To administer the treatment advanced stereotactic radiotherapy equipment moves around the patient's head to target radiation, with millimetre precision, to tumours deep within the brain. This involves the use of a specially designed head frame which is made to the exact measurements of the patient and is painlessly strapped to the head, without the need for an anaesthetic - another feature of the new treatment.
Since the frame can be removed and re-fitted easily, the treatment can be 'fractionated' - or delivered in small doses over a period of time rather than given in one block, as with previous forms of radiosurgery. In addition to making the experience more comfortable for the patient, the fractionation method is less damaging to normal brain tissue when compared with single dose treatment.
Standard methods of radiotherapy involve geometrical beams which form a box around a tumour, damaging surrounding tissue and leaving permanent side effects. Using conformal radiotherapy techniques, developed at The Royal Marsden and The Institute, the radiation beams can be shaped to mimic exactly the irregular form of a tumour.
In order to vary the intensity of dosage across each part of the tumour, the intensity modulated radiotherapy (IMRT) technique can be applied. Beams are delivered through special robotic 'leaves' known as multi-leaf collimators. These move constantly during delivery of the beam in order to tailor irradiation dosage to different areas.
The treatment is particularly suitable for skull base tumours where critical areas such as the brain stem and regions controlling the central nervous system lie very close to the tumour.
Dr Brada's teams at The Institute and The Royal Marsden are currently working on further refinements to the technique so that oncology units nationally and internationally can easily adapt their existing standard radiotherapy equipment to accommodate the new developments.
Notes
- The first patients were treated with this technique in 1995. 30 children and 83 adults with localised brain tumours took part.
- A research nurse for the study was funded by The Cancer Research UK.