Proton RBE models: commonalities and differences.

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiobiology

Background:

• Relative biological effectiveness (RBE) of protons is crucial for optimizing proton therapy.
• Current treatment planning often uses a fixed RBE of 1.1, despite preclinical data showing variability.
• Existing phenomenological models for proton RBE show poor agreement, hindering clinical application.

Purpose of the Study:

• To investigate conceptual agreement and disagreement among different proton RBE models.
• To identify key parameters driving discrepancies between these models.
• To guide future research for more accurate RBE modeling in proton therapy.

Main Methods:

• Comparative analysis of phenomenological proton RBE models.
• Evaluation of model predictions across varying biological and physical parameters.
• Focus on linear energy transfer (LET) dependence and linear-quadratic model parameters (α and β).

Main Results:

• Primary model disagreements stem from the handling of biological parameters (α and β) from the linear-quadratic model.
• All models demonstrate strong correlation when analyzed for dependence on linear energy transfer (LET).
• Conceptual agreement is observed regarding LET-dependence, but differences in biological parameter handling persist.

Conclusions:

• Systematic exploration of biological variation in RBE is needed.
• Well-controlled studies across diverse cell types are essential.
• Distinguishing between models requires a focus on biological parameter differences and validation against experimental data.