Does the FLASH sparing effect occur in human normal tissue
In plain words
The tissue-protecting effect of ultra-fast radiation has been shown mostly in mice and other animals. Whether it happens in people at clinically useful doses has not been measured.
Precise statement
Determine whether single-fraction doses of 800 to 3000 rad delivered at mean dose rates above 4000 rad/s produce measurably lower normal-tissue toxicity in humans than the same dose at conventional dose rates of 1 to 10 rad/s, at matched tumour control, for at least one tissue and endpoint. An answer is yes or no with an estimated dose-modifying factor and confidence interval.
What would settle it
A randomized clinical comparison of FLASH and conventional dose rate at equal dose with a prespecified normal-tissue endpoint.
Status in the literature
The FAST-01 trial (Mascia et al., JAMA Oncology 2023) showed feasibility of proton FLASH at 800 rad in 10 patients with bone metastases, with no conventional-dose-rate comparison arm; no randomized toxicity comparison was found in the sources checked.