RapidPlan hippocampal sparing whole brain model version 2-how far can we reduce the dose?

Area of Science:

• Radiation Oncology
• Medical Physics
• Neuro-oncology

Background:

• Whole-brain radiotherapy (WBRT) is a standard palliative treatment for brain metastases.
• Limiting hippocampal radiation dose is crucial for reducing cognitive side effects.
• Existing Knowledge Based Planning (KBP) models for WBRT can be further optimized for hippocampal sparing.

Purpose of the Study:

• To update an existing KBP model to further reduce hippocampal radiation dose.
• To improve overall dosimetric quality of WBRT treatment plans.
• To validate the updated model on different radiotherapy platforms.

Main Methods:

• An existing KBP model was updated using a recursive training process to create the Hippocampal Sparing Whole Brain Version 2 (HSWBv2) model.
• Forty-two clinical cases were used for model development and re-planning.
• A new dosimetric scorecard was developed to objectively assess plan quality.
• Plans generated by HSWBv2 were compared against the previous model (HSWBv1) on Varian Halcyon™ and TrueBeam™ systems.

Main Results:

• HSWBv2 significantly reduced hippocampal dose (D100%, Dmean, D0.03cc) compared to HSWBv1 (p < 0.001).
• Improvements were observed in target coverage (PTV_3000 D98%) and dose conformity (PTV_3000 V105% reduced from 35.35% to 6.44%, p < 0.001).
• Dosimetric improvements were validated on additional cases and on the TrueBeam™ platform.

Conclusions:

• The HSWBv2 model achieves superior hippocampal avoidance WBRT plans with reduced hippocampal dose.
• The updated model improves target coverage and dose conformity/homogeneity.
• HSWBv2 offers enhanced treatment planning for WBRT, with the model being publicly shared.