Uncovering the Protective Neurologic Mechanisms of Hypofractionated FLASH Radiotherapy

Area of Science:

• Radiation Oncology
• Neuroscience
• Cancer Therapy

Background:

• Ultra-high dose-rate FLASH radiotherapy (FLASH-RT) shows promise for reducing normal tissue toxicity while maintaining efficacy.
• Understanding the mechanisms behind FLASH-RT's neuroprotective effects is crucial for clinical translation.

Purpose of the Study:

• To evaluate the differential neurologic responses to whole brain FLASH-RT versus conventional dose rate radiotherapy (CONV-RT) in mice.
• To investigate the functional and molecular outcomes related to cognition, synaptic plasticity, and neuroinflammation over a 6-month period.

Main Methods:

• Non-tumor-bearing male and female mice were exposed to hypofractionated (3 × 10 Gy) whole brain FLASH-RT and CONV-RT.
• Comprehensive behavioral testing assessed cognitive indices of learning and memory.
• Synaptic plasticity was measured by long-term potentiation (LTP); molecular markers of synaptic integrity and neuroinflammation were analyzed.

Main Results:

• FLASH-RT preserved cognitive function, including learning and memory, unlike CONV-RT.
• Cognitive preservation correlated with protected synaptic plasticity (LTP).
• FLASH-RT reduced neuroinflammation (CD68+ microglia) and preserved synaptic integrity (synaptophysin) in key brain regions (hippocampus, medial prefrontal cortex).

Conclusions:

• Hypofractionated FLASH-RT functionally preserves cognition and synaptic plasticity in the brain.
• Neuroprotection by FLASH-RT is associated with reduced neuroinflammation and preserved synaptic integrity.
• These findings provide a mechanistic basis for FLASH-RT's reduced normal tissue complications in the brain.