Treatment planning for in vivo multi-fraction, multi-port, multi-modal Synchrotron Radiotherapy.

Area of Science:

• Medical Physics
• Radiation Oncology
• Preclinical Cancer Research

Background:

• Treatment planning systems (TPSs) for microbeam radiotherapy (MRT) require enhancement for complex in-vivo studies.
• Existing literature lacks detailed dosimetry and planning data for linking MRT dose to treatment outcomes.
• This study addresses these gaps by detailing a synchrotron-based, fractionated MRT approach in tumor-bearing mice.

Purpose of the Study:

• To detail dosimetry, treatment planning, delivery, and evaluation for in-vivo microbeam radiotherapy (MRT) studies.
• To correlate physical dose with observed treatment outcomes in a preclinical model.
• To adapt and utilize the Eclipse TPS for fractionated, mixed-modality synchrotron radiotherapy.

Main Methods:

• Adapted the Eclipse TPS to accumulate dose for fractionated mixed-modality treatments.
• Employed manual plan optimization to meet dose prescriptions and constraints.
• Calculated and compared volumetric dose data for tumors, organs-at-risk, and metastases to treatment outcomes.

Main Results:

• Manual plan optimization met most requirements, limited by delivery system constraints.
• Dose accumulation for BB and MRT valleys was achieved; MRT peaks were assessed separately.
• Tumor control was maintained; primary tumor volume reduced by >32% with MRT, but metastases were not controlled. Temporal beam placement did not alter outcomes.

Conclusions:

• This work details the first use of Eclipse TPS for multi-fraction, multi-port, mixed-modality synchrotron radiotherapy.
• Provides crucial insights into treatment outcomes and biological endpoints relative to physical dose in MRT.
• Highlights the need for advanced TPS capabilities in preclinical MRT research.