LET-painting increases tumour control probability in hypoxic tumours

Area of Science:

• Radiation Oncology
• Medical Physics

Background:

• Tumor hypoxia is a significant challenge in radiation therapy, leading to treatment resistance.
• High linear energy transfer (LET) radiation can overcome hypoxia but increases normal tissue toxicity.
• LET-painting aims to deliver high-LET radiation to hypoxic tumor regions while sparing normoxic tissues.

Purpose of the Study:

• To evaluate the efficacy of LET-painting using carbon-12 and oxygen-16 ions for treating hypoxic oropharyngeal cancer.
• To determine the threshold hypoxic tumor volume for effective treatment with LET-painting.
• To assess the impact of a dose boost on tumor control probability (TCP) in hypoxic subvolumes.

Main Methods:

• Developed carbon-12 and oxygen-16 ion treatment plans for an oropharyngeal cancer case with a hypoxic component.
• Optimized target dose for 95% TCP assuming normoxic tissue.
• Recalculated TCP using LET-painting, varying hypoxic volumes, and incorporating a dose boost.

Main Results:

• LET-painting with carbon-12 ions achieved tumor control only for hypoxic subvolumes < 0.5 cm³.
• Oxygen-16 ion LET-painting enabled tumor control for hypoxic subvolumes up to 1-2 cm³.
• A combination of oxygen-16 LET-painting and a dose boost improved tumor control for larger hypoxic subvolumes.

Conclusions:

• LET-painting with oxygen-16 ions significantly enhances tumor control in hypoxic tumors.
• A modest dose boost in conjunction with LET-painting further improves outcomes for larger hypoxic regions.
• Oxygen-16 ion LET-painting represents a promising strategy for improving radiotherapy in hypoxic cancers.