The use of charged particles as an alternative to x-ray or gamma ray radiation can extend the scope of radiotherapy to tumours previously requiring invasive surgery, while speeding up diagnosis and reducing collateral damage to surrounding tissue.
This fast emerging field of charged particle cancer therapy was thrashed out at a recent workshop organised by the European Science Foundation (ESF), which discussed new instruments that will lead to improvements in both diagnosis and treatment. Diagnosis and treatment are closely linked in radiotherapy, since more accurate location of tumour cells in turn enables the radiation dose to be more precisely focused.
"Developments in imaging have allowed improvements in radiation beam placement, and the two areas tend to go together," said Barbara Camanzi, convenor of the ESF workshop, and specialist in radiotherapy instrumentation at the Rutherford Appleton Laboratory Department of Particle Physics near Oxford in the UK. This in turn improves prospects of destroying the tumour while reducing collateral damage to healthy tissue nearby. Such collateral damage causes not just tissue death, but can lead to induction of secondary tumours, which has been a long standing problem for traditional radiotherapy using x rays. Some tissue cells close to the tumour receive enough radiation to trigger mutations in their DNA that can cause them to become malignant, but not enough radiation to kill them.
"The fall in collateral radiation deposition in the body ranges from a factor of 2 to 15 depending on the precise treatment indication and body site," noted Bleddyn Jones, an oncologist attending the ESF workshop, from the Gray Institute for Radiation Oncology and Biology in Oxford, UK. "All techniques using external gamma rays and x-rays impart a larger dose to surrounding healthy tissue with long term risks of functional changes and malignant induction."
The improved imaging made possible by use of charged particles also makes it easier to detect tumours when they are small, improving prospects for patients whether or not they actually undergo radiotherapy. "Making an earlier diagnosis of a smaller cancer increases the chance of cure following either particle beam therapy or surgery," said Camanzi.
However, the ESF workshop identified that further significant improvements in instrumentation were required, both for treatment and diagnosis, to exploit the full potential of charged particles for cancer therapy. Further work was also required to adjust dose to minimise the risk of secondary tumour formation caused by the radiation, which remains a risk with use of charged particles. The ESF workshop also addressed the need for improved design of the gantry systems used both for imaging and to deliver the radiation doses in treatment.
The other important issue addressed by the ESF workshop is educating radiotherapy consultants in the new techniques so that they are in a position to determine the best form of treatment for each individual case. Sometimes charged therapy may be the best method, in other cases traditional x-ray therapy, and in yet others surgery or chemotherapy, or combinations of these.
"There is a need to hold more educational and training meetings on particle therapy especially in those European countries that at present have no plans for such facilities," said Camanzi, who noted that a follow up symposium in Oxford had been proposed for 2010.
Thomas Lau | alfa
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