A role for biological optimization within the current treatment planning paradigm

Area of Science:

• Radiation Oncology
• Medical Physics
• Cancer Treatment Planning

Background:

• Intensity modulated radiotherapy (IMRT) planning offers potential for reducing radiation-induced toxicity through biological optimization.
• Clinical adoption of biological optimization is limited due to reliance on physical dose-volume constraints.
• A novel approach integrates biological optimization post-dose-volume optimization to enhance plan quality.

Purpose of the Study:

• To introduce and evaluate a method for incorporating biological optimization after dose-volume constrained optimization (DVO).
• To improve radiation dose distribution by reducing biological toxicity metrics without compromising DVO achievements.
• To assess the efficacy of this integrated approach in clinical scenarios.

Main Methods:

• Clinicians identify 'fixed points' on dose-volume histograms representing critical DVO qualities.
• Biological optimization iteratively reduces biological metrics (e.g., equivalent uniform dose - EUD) while respecting fixed points.
• The method is demonstrated in prostate cancer and olfactory neuroblastoma cases, compared against purely biological optimization.

Main Results:

• Biological optimization post-DVO further reduced normal organ doses, particularly high doses, in both study cases.
• Prostate case: Bladder/rectum EUDs reduced by 5.0%/3.9%, highest doses by 4.6%/7.8%.
• Olfactory neuroblastoma case: Significant EUD and highest dose reductions observed in surrounding organs like eyes and optic nerves.

Conclusions:

• Integrating biological optimization after DVO effectively reduces biological toxicity metrics.
• This approach preserves the benefits of DVO while enhancing overall plan quality.
• The proposed method is compatible with current clinical IMRT planning practices and expectations.