Mid-range arc therapy for efficient and RBE-robust proton treatment.

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Planning

Background:

• Proton arc therapy (PAT) presents challenges in clinical translation due to radiobiological uncertainties and delivery inefficiencies.
• Existing methods require optimization for improved plan conformity and normal tissue sparing.

Purpose of the Study:

• Introduce Mid-Range Proton Arc Therapy (MRPAT), a novel planning approach for PAT.
• Enhance delivery efficiency and mitigate range-related uncertainties in proton therapy.

Main Methods:

• MRPAT utilizes a single mid-range energy layer (MREL) per beam direction, placing the Bragg peak centrally within the target.
• Investigated feasibility using an ellipse phantom and clinical cases (prostate, spine, head and neck).
• Compared physical dose, LETd, RBE-weighted dose, and delivery efficiency against Full-Arc and intensity-modulated proton therapy (IMPT).

Main Results:

• MRPAT achieved comparable target coverage and OAR sparing to Full-Arc plans, indicating energy layer redundancy.
• Effectively confined high LETd and RBE hotspots to the target center, reducing spillage.
• MRPAT significantly improved delivery efficiency, reducing beam delivery time by approximately 80% compared to Full-Arc.

Conclusions:

• MRPAT is a simple, efficient planning concept for PAT.
• Demonstrates practical clinical utility and adaptability for future adaptive radiotherapy workflows.
• Effectively contains high dose-gradient regions, improving safety and efficacy.