Relative Biological Effectiveness-Clinical Practice at US Proton Therapy Centers

Area of Science:

• Radiation Oncology
• Medical Physics

Background:

• Proton therapy offers superior dose distribution but relies on a generic relative biological effectiveness (RBE) of 1.1 for treatment planning.
• Emerging evidence indicates RBE varies with dose, linear energy transfer (LET), and biological endpoints, potentially leading to underestimation of RBE-weighted dose.

Purpose of the Study:

• To assess awareness and management of RBE variability in clinical practice within US proton therapy centers.
• To identify current practices and future needs regarding RBE in proton therapy.

Main Methods:

• A survey with 32 questions was distributed to 29 US proton therapy centers via the Particle Therapy Co-Operative Group - North America.
• The survey covered awareness of RBE variability, practices to account for it, and future requirements.

Main Results:

• An 80% response rate revealed significant apprehension regarding the assumption of a constant RBE of 1.1.
• Centers report toxicities and recurrences potentially linked to RBE underestimation, despite using a fixed RBE of 1.1.
• Nearly all centers consider RBE variability in beam arrangement; some perform LET and variable RBE calculations.

Conclusions:

• There is a strong consensus on the need for multi-institutional databases, clinical evidence accumulation, and education on proton RBE.
• Standardized approaches are lacking, leading to inconsistencies in proton therapy planning.
• Developing consensus guidelines and integrating advanced RBE/LET models can enhance proton therapy precision and safety.