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Background

Recent advances in radiation biology and preclinical research have identified that high doses of radiation at ultra-high dose rate can lead to sparing of normal tissue, while maintaining tumor control. This has been termed the FLASH effect and has been extended from electrons to protons, heavy ions and photons. Lung cancer treatments, despite the advancements in radiotherapy with precise protons, are still associated with significant damage to the normal tissue. FLASH proton exposures have not been characterized yet with regards to lung tissue injury or sparing.

Methods

In this pilot study we used precision cut lung slices from human healthy non-smoker donors, two male and one female, and exposed this ex vivo model to a single dose of 12 Gy of standard or FLASH protons and analyzed them with untargeted metabolomics at 24 h after exposure.

Results

We identified 22 metabolites of interest, with primary enrichment in β-alanine metabolism, sphingolipid metabolism, primary bile acid biosynthesis, and one carbon pool by folate, while chemical classes showed that sphingoid bases and eicosanoids were two of the most enriched chemical classes after radiation exposure. Classification analysis with receiver operating characteristic curves based on the 22 metabolites indicated the presence of individual variability to responses, that warrant future studies with a larger cohort.

Conclusions

Although this is a pilot study, we show the utility of ex vivo models in radiation research and particularly with standard and FLASH protons, and that further research in this area should include both male and female subjects. This ex vivo human model should therefore be investigated further to identify early responses to proton exposures.