Cancer patients needing proton therapy could benefit from more effective treatment after scientists in Norway discovered that light-activated drugs transform the treatment.
A study by scientists at Oslo University Hospital has demonstrated the activation of light-sensitive drugs by accelerated protons.
Photosensitisers (PSs) have normally been used in clinical settings with activation by visible light in photodynamic therapy (PDT).
Although PSs accumulate in tumours because of local destruction of the blood/brain barrier at the tumour site, when the drugs interact with light, they create toxic oxygen by-products that kill the cancerous tissues around them.
Clinics use protons in radiation therapy for hard-to-reach tumours because they deeply penetrate tissue and accurately deliver their energy to a tumour.
In this study, led by Dr Theodossis Theodossiou, from the Department of Radiation Biology, Institute for Cancer Research, Norwegian Radium Hospital, Oslo University Hospital, scientists activated protons to activate PSs and generate the therapeutic by-products of oxygen.
They observed the emission of fluorescence as well as the production of toxic singlet oxygen when numerous PSs were irradiated by accelerated protons at the cyclotron accelerator. The findings, published in Nature Communications, could lead to more effective, cancer-specific proton therapy through the additional administration of a photosensitiser.
Dr Theodossiou said: “We predicted that this would happen as the positively charged protons were quite likely to interact with the negatively charged electrons on their path, especially in chemical systems rich in electrons, such as PSs.
Dr Mantas Grigalavicius, a member of the Protonics team, added: “It was a very intensive effort with very demanding experiments and the need for continuous thinking for custom-made technical and scientific solutions, and it was heavily dependent on the availability of the proton beam, but we finally made it.”
They now hope that the first in-human trial could be performed in the proton centre that is being built on the university campus and could be operational in two to three years.
The new treatment’s potential was initially tested in cultured brain-cancer cells, a trial that found that more tumour cells died when a PS was added to proton irradiation.
Grigalavicius M et al. Proton-dynamic therapy following photosensitiser activation by accelerated protons demonstrated through fluorescence and singlet oxygen production, Nature Communications 4 September 2019; doi: 10.1038/s41467-019-12042-7
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