Biological optimization of tumor radiosurgery

Area of Science:

• Medical Physics
• Radiation Oncology
• Mathematical Biology

Background:

• Tumor radiosurgery involves delivering high radiation doses in a single session.
• Selecting irradiation strategies for high biological efficiency is crucial.
• Understanding the impact of dose heterogeneity and delivery rate is essential.

Purpose of the Study:

• To develop a mathematical framework for investigating biological effects of dose heterogeneity and delivery rate in radiosurgery.
• To optimize dose distribution and delivery parameters for improved treatment outcomes.

Main Methods:

• Simulated a target with proliferating, hypoxic tumor cells, and normal tissue.
• Evaluated treatment outcome using a functional of dose distribution (LQ-surviving fractions).
• Employed calculus of variation techniques for biological optimization with constraints on intensity, homogeneity, and duration.

Main Results:

• Increased dose heterogeneity significantly improved biological performance for a fixed dose.
• Dose distribution concentrated in hypoxic and proliferating tumor areas, reducing normal tissue damage.
• Optimized delivery duration (1-30 min) coincided with maximum allowed values, yielding poor therapeutic gain.
• Therapeutic gain was positively correlated with the tumor/normal DNA repair time ratio.

Conclusions:

• The developed mathematical framework enables designing biologically optimized dose distributions and dose rates for tumor radiosurgery.
• This framework can be integrated into simulation software to aid treatment planning.
• Heterogeneity in dose delivery is a key factor for enhancing biological efficiency in radiosurgery.