Automatic replanning of VMAT plans for different treatment machines: A template-based approach using constrained...

Area of Science:

• Radiation Oncology
• Medical Physics
• Cancer Treatment Planning

Background:

• Machine breakdowns necessitate rapid replanning for radiotherapy.
• Transferring treatment plans between different linear accelerator models presents challenges.
• Existing methods for plan adaptation can be time-consuming and complex.

Purpose of the Study:

• To evaluate a novel automatic template-based replanning approach for volumetric modulated arc therapy (VMAT).
• To assess the feasibility of rapid plan transfer for prostate cancer (PC) and head-and-neck cancer (HNC) cases.
• To combine automatic replanning with constrained optimization for efficient plan adaptation.

Main Methods:

• Utilized constraints from existing VMAT plans as templates for reoptimization on different accelerator head models.
• Employed the Hyperion treatment planning system (TPS) for plan generation.
• Performed automatic replanning for 16 PC cases (MLC1 to MLC2/MLC3) and 19 HNC cases (MLC2 to MLC3), evaluating target and organ-at-risk (OAR) dose metrics.

Main Results:

• All 16 PC cases were successfully replanned with minimal target EUD deviation (mean -0.15% to -0.57%).
• OAR sparing was achieved in all PC cases.
• 16 out of 19 HNC cases were successfully replanned, maintaining OAR sparing and showing a mean decrease in PTV60 EUD of -0.64%.

Conclusions:

• Automatic replanning using pre-existing VMAT plan constraints as templates is feasible for adapting plans to different treatment machines.
• This method successfully maintains plan quality and constraint compliance.
• The approach facilitates rapid and reliable plan transfer, crucial for managing machine downtime.