Proton and ion beams exhibit better dose characteristics than x-rays for radiotherapy. Their superiority lies in the fact that the radiation dose can be confined largely to the tumour with much lower doses to the surrounding healthy tissue than can be achieved with x-rays. This allows for dose escalation in the tumour itself and therefore better control of the treatment outcome or far more sparing of dose to critical organs.
Proton and ion beam therapy is not new, having first been proposed in 1946, however in recent year’s improvements in the technology has meant it has become much cheaper and proton therapy can now be delivered at approaching twice the cost of x-ray therapy.
Emerging new accelerator technologies such as laser induced beams, dielectric wall accelerators and fixed field alternating gradient accelerators promise lowering the price tag even further.
The NHS has increased support for proton therapy by sending patients abroad as a transitory solution and by committing to support two large-scale proton therapy facilities. These are sited at the Christie Hospital in Manchester, which started treating patients at the end of 2018 and University College London Hospital which is due to come on line by 2020.
In order to make the most of this modality (optimal treatment outcome with minimal side effects) dosimetric accuracy similar to that currently achieved in x-ray therapy is required and improved primary standards and reference dosimetry is needed.