FLASH radiotherapy is a promising new technique that uses high-energy particles to treat tumours; a high dose of radiation is administered almost instantaneously – in milliseconds rather than around a minute. Here, the tumour tissue is damaged in the same manner as with conventional radiotherapy; however it is believed that healthy tissue is less affected, meaning that less side effects are expected.
The aim is a step change in cancer treatment, and there is a growing interest in the proton therapy community, with early tests indicating that the FLASH effect is present with high dose rate proton irradiation as has been observed with conventional X-ray treatments.
CI expert Dr Hywel Owen from The University of Manchester – and co-author of a paper that has just been published in Physica Medica (the European Journal of Medical Physic) which focuses on the technological challenges of FLASH proton therapy, said: “In order to deliver protons at clinically relevant dose rates for FLASH, significant technical hurdles must be overcome in the accelerator technology. Of these challenges, increasing the average current from the present clinical range of 0.1-10 nA to in excess of 100 nA seems feasible with some existing systems, but providing rapid energy adjustment is much more challenging.”
The delivery of FLASH proton therapy requires significant advances in accelerator, magnet, beam diagnostics and dosimetry technology. Researchers across the CI institutions are working on these. Different accelerator types are being considered for the delivery of the proton beam and each one has its own challenges in order to meet this goal.
In the study, which was supported by the EU-funded research network OMA, the authors conclude that the most direct route to a clinical FLASH proton system appears to be with an isochronous cyclotron utilizing a hybrid spot-scanned approach.
However, significant changes in the mode of operation or treatment using either this accelerator type, or instead using synchrotrons or linear accelerators, will be needed in order to enable a fully-fledged FLASH system. To design optimal technology for such a system, further studies are also required on the biological and clinical issues; the CI is engaged in several international collaborations with industrial partners to realise this goal.
Further information
S. Jolly et al., “Technical challenges for FLASH proton therapy”, Physica Medica – EJMP 78, p71-82 (2020), DOI: https://doi.org/10.1016/j.ejmp.2020.08.005