What is the Mechanism behind FLASH Dose Rate Effect?

Presenting author:
Jian-Yue Jin, PhD

By Jing Wang, PhD, UT Southwestern Medical Center

By delivering radiation in ultra-high dose rates, FLASH radiation therapy (FLASH-RT) has shown improved therapeutic ratio in many preclinical studies with improved normal tissue sparing while maintaining the same tumor killing effect as compared to the radiation delivered with conventional dose rates. While FLASH-RT can potentially change the paradigm of RT, the biological mechanism behind the FLASH effect is largely unknown. Different mechanisms have been suggested to explain the FLASH effect, such as oxygen depletion and modified immune response.

In the work FLASH Dose Rate Effect on Circulating Immune Cells: A Potential Mechanism for FLASH-RT?, the authors examined, through a computational study, one potential factor that could contribute to the modified immune response which eventually leads to the FLASH effect: reduced circulating immune cells killing at FLASH dose rate. By modeling irradiated blood volume and the extent of killing of circulating immune cells at FLASH vs. conventional dose rates, the authors determined the threshold FLASH dose rate was about 40 Gy/second for mice in an average situation, which is consistent with the reported FLASH dose rate in animal studies. The computation results also show that the threshold FLASH dose rate for humans is about one order of magnitude less than that for mice.

While more thorough investigations are needed, the results presented in this work suggest the alleviation of stringent dose rate requirements in a clinical FLASH-RT system.

FLASH Dose Rate Effect on Circulating Immune Cells: A Potential Mechanism for FLASH-RT? was presented on Saturday, October 24, in the Science Center, as part of Scientific session (SS) 02.

Published on: October 25, 2020


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