Calculating Variations in Biological Effectiveness for a 62 MeV Proton Beam

Area of Science:

• Biophysics
• Radiation Oncology
• Cell Biology

Background:

• Radiation-induced cell death and chromosome aberrations are critical endpoints in radiotherapy.
• Understanding DNA damage mechanisms is key to optimizing radiation therapy.
• Accurate modeling of radiation effects is essential for treatment planning.

Purpose of the Study:

• To develop and apply the BIophysical ANalysis of Cell death and chromosome Aberrations (BIANCA) model to therapeutic protons.
• To investigate DNA cluster damage as a pivotal mechanism for cell death and aberrations.
• To predict cell death and chromosome aberrations along proton Bragg peaks and evaluate beam effectiveness.

Main Methods:

• Developed and implemented the BIANCA model as a Monte Carlo (MC) code.
• Applied the model to pristine and modulated proton beams for eye melanoma treatment.
• Validated the model by reproducing experimental survival curves for AG01522 cells.
• Predicted cell death and aberrations for AG01522 and V79 cells at various depths in a spread-out Bragg peak (SOBP).

Main Results:

• The BIANCA model successfully reproduced experimental survival data for AG01522 cells.
• Cell death and chromosome aberrations increased along the SOBP plateau and beyond the distal fall-off.
• The model predicted significant damage beyond the intended target area due to low-energy protons.
• The study highlighted that a constant relative biological effectiveness (RBE) assumption along a proton SOBP may be suboptimal.

Conclusions:

• The BIANCA model provides a robust biophysical approach to characterize therapeutic proton beams.
• The findings suggest that RBE varies along the proton beam path, necessitating individualized treatment planning.
• This modeling approach offers a way to evaluate beam effectiveness without relying on experimental RBE values, reducing uncertainties.