Radiotherapy debut for proton linac

9 January 2023
The LIGHT accelerator at STFC Daresbury Lab
Compact treatment The LIGHT accelerator at STFC Daresbury Laboratory, UK. Credit: AVO

Hadron therapy, to which particle and accelerator physicists have contributed significantly during the past decades, has treated more than 300,000 patients to date. As collaborations and projects have grown over time, new methods aimed at improving and democratising this type of cancer treatment have emerged. Among them, therapy with proton beams from circular accelerators stands out as a particularly effective treatment: protons can obliterate tumours, sparing the surrounding healthy tissues at higher rates than conventional electron or photon therapy. Unfortunately, present proton- and ion-therapy centres are large and very demanding on the design of buildings, accelerators and gantry systems.

A novel proton accelerator for cancer treatment based on CERN technology is preparing to receive its first patients in the UK. Advanced Oncotherapy (AVO), based in London, has developed a proton-therapy system called LIGHT (Linac Image-Guided Hadron Technology) – the result of more than 20 years of work at CERN and spin-off company ADAM, founded in 2007 to build and test linacs for medical purposes and now AVO’s Geneva-based subsidiary. LIGHT provides a proton beam that allows the delivery of ultra-high dose rates to deep-seated tumours. The initial acceleration to 5 MeV is based on radio-frequency quadrupole (RFQ) technology developed at CERN and supported by CERN’s knowledge transfer group. LIGHT reached the maximum treatment energy of 230 MeV at the STFC Daresbury site on 26 September. Four years after the first 16 m-long prototype was built and tested at LHC Point 2, this novel oncological linac will treat its first patients in collaboration with University Hospital Birmingham at Daresbury during the second half of 2023, marking the first time a proton linear accelerator is used for cancer therapy.

LIGHT operates with components and designs developed by CERN, ENEA, the TERA Foundation and ADAM. Components of note include LIGHT’s RFQ, which contributes to its compact design, as well as 19 radio-frequency modules composed of four side-coupled drift-tube accelerating cavities based on a TERA Foundation design and 15 coupled accelerating cavities with industrial design by ADAM. Each module is controlled to vary the beam energy electronically, 200 times per second, depending on the depth of the tumour layer. This obviates the need for absorbers (or degraders), which greatly reduce the throughput of protons and produce large unwanted radiation, therefore reducing the volume of shielding material required. This design allows the linear accelerator to generate an extremely focused beam of 70 to 230 MeV and to target tumours in three dimensions, by varying the depth at which the radiation dose is delivered much faster than existing circular accelerators.

“Our mission is simple: democratise proton therapy,” says Nicolas Serandour, CEO of AVO. “The only way to fulfill this goal is through the development of a different particle accelerator and this is what we have achieved with the successful testing of the first-ever proton linear accelerator for medical purposes. Importantly, the excitement comes from the fact that cost reduction can be accompanied with better medical outcomes due to the quality of the LIGHT beam, particularly for cancers that still have a low prognosis. I cannot over-emphasise the importance that CERN and ADAM played in making this project a tangible reality for millions of cancer patients.” 

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