Hypoxia imaging and radiotherapy: bridging the resolution gap.

Area of Science:

• Radiation oncology
• Medical imaging
• Tumor microenvironment

Background:

• Oxygen levels critically influence radiotherapy efficacy; well-oxygenated tumors respond better than hypoxic ones.
• Tumor hypoxia correlates with treatment resistance and poor patient prognosis.
• Tumor oxygenation is heterogeneous and challenging to measure directly.

Purpose of the Study:

• To review the radiobiological oxygen effect and its implications for radiotherapy.
• To discuss functional hypoxia imaging, particularly fluorine-18 fluoromisonidazole positron emission tomography (¹⁸F-FMISO PET).
• To examine the concept and challenges of hypoxia-guided dose painting in radiotherapy.

Main Methods:

• Review of mechanistic basis of the radiobiological oxygen effect.
• Analysis of factors contributing to microscopic heterogeneity in tumor oxygenation.
• Evaluation of current hypoxia imaging modalities and their limitations.
• Discussion of dose-painting strategies and future challenges.

Main Results:

• Hypoxia significantly reduces tumor response to radiotherapy.
• ¹⁸F-FMISO PET shows potential for non-invasive assessment of tumor hypoxia.
• Significant scale discrepancies exist between imaging resolution, oxygen distribution, and treatment delivery scales.

Conclusions:

• Hypoxia dose painting offers a promising strategy to overcome radioresistance.
• Addressing scale-dependent challenges in imaging and treatment delivery is crucial for successful implementation.
• Further research is needed to optimize hypoxia-guided radiotherapy paradigms.