A Gaussian-Based Planning Approach for Robust Dose-Escalated Stereotactic Body Proton Therapy

Area of Science:

• Radiation Oncology
• Medical Physics
• Cancer Treatment

Background:

• Proton therapy plans often lack the dose heterogeneity seen in photon SBRT.
• This homogeneity may limit the effectiveness of proton therapy for ablative treatments.
• Stereotactic body proton therapy (SBPT) requires planning strategies to optimize dose distribution.

Purpose of the Study:

• To develop and evaluate a novel treatment planning approach for SBPT.
• The goal is to replicate photon SBRT dose characteristics, including high central doses and rapid falloff.
• This aims to improve dose escalation potential and clinical data harmonization.

Main Methods:

• A semi-automated Gaussian-based planning technique was developed.
• The technique divides the gross tumor volume (GTV) into shells to shape dose falloff.
• The method was tested on 10 liver SBPT patients, comparing Gaussian plans to standard homogeneous plans.

Main Results:

• Gaussian plans achieved hotspots within 2.2% of target values.
• Biologically effective dose significantly increased by 20 Gy (α/β=10) compared to homogeneous plans.
• While PTV dose spill was slightly higher, Gaussian plans showed lower gastrointestinal organ-at-risk doses and a trend for lower mean liver dose.

Conclusions:

• A novel, mathematically driven technique for liver SBPT planning was successfully developed and tested.
• The Gaussian approach effectively mimics photon SBRT dose distributions.
• This technique may enable safe dose escalation and better integration with existing SBRT clinical data.