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Updated: Jul 2, 2025
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Tumor Hypoxia Assessment: In Vivo 3D Oxygen Imaging Through Electron Paramagnetic Resonance
Published on: February 14, 2025
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Acute Hypoxia Does Not Alter Tumor Sensitivity to FLASH Radiation Therapy
Ron J Leavitt1, Aymeric Almeida1, Veljko Grilj2
1Radiation Oncology Laboratory, Department of Radiation Oncology, Lausanne, University Hospital and University of Lausanne, Lausanne, Switzerland.
International Journal of Radiation Oncology, Biology, Physics
|February 22, 2024
Summary
FLASH radiotherapy maintains its tumor-killing effectiveness even in low-oxygen conditions, overcoming treatment resistance. This approach offers benefits over conventional radiation therapy, especially for radioresistant tumors.
Area of Science:
- Oncology
- Radiation Oncology
- Cancer Biology
Background:
- Tumor hypoxia is a significant factor contributing to resistance against conventional dose rate (CONV) radiation therapy.
- Understanding the impact of hypoxia on novel radiation techniques is crucial for improving cancer treatment outcomes.
Purpose of the Study:
- To evaluate the efficacy of ultra-high dose rate (FLASH) radiation therapy in overcoming hypoxia-mediated tumor resistance.
- To compare the effectiveness of FLASH versus CONV radiation therapy under hypoxic conditions.
Main Methods:
- Subcutaneous tumor models (glioblastoma, head and neck cancer, lung adenocarcinoma) were established in mice.
- Tumors were subjected to a single 20-Gy fraction using either CONV or FLASH irradiation.
- Tumor oxygen tension, growth, and molecular profiles (RNAseq, pimonidazole) were analyzed; glycolysis was inhibited with trametinib in GBM models.
Main Results:
- FLASH radiation therapy demonstrated significant antitumor efficacy in hypoxic tumors, unlike CONV radiation.
- Molecular analysis revealed FLASH-specific changes in glioblastoma, including cell-cycle arrest and a metabolic shift towards glycolysis.
- Inhibition of glycolysis with trametinib enhanced FLASH efficacy in both normoxic and hypoxic conditions.
Conclusions:
- FLASH radiation therapy is effective in overcoming hypoxia-induced resistance, offering an advantage over CONV radiation.
- These findings highlight FLASH radiotherapy's potential as a more effective treatment modality for radioresistant tumors.
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