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Robust mixed electron-photon radiation therapy planning for soft tissue sarcoma
Veng Jean Heng1, Monica Serban2,3, Marc-André Renaud4
1Department of Physics and Medical Physics Unit, McGill University, Montreal, Canada.
Medical Physics
|September 8, 2023
Summary
Mixed electron-photon beam radiation therapy (MBRT) spares organs at risk for soft tissue sarcoma patients. This advanced technique offers dosimetric benefits without compromising target coverage compared to VMAT.
Area of Science:
- Radiation Oncology
- Medical Physics
Background:
- Mixed electron-photon beam radiation therapy (MBRT) combines electron and photon beams for optimized radiation treatment plans.
- MBRT leverages the dose falloff of electrons and the sharp penumbra of photons.
Purpose of the Study:
- To investigate the dosimetric advantages of MBRT for soft tissue sarcoma (STS) patients.
- Compare MBRT plans against conventional photon-based Volumetric Modulated Arc Therapy (VMAT).
Main Methods:
- Retrospective replanning of 22 lower extremity STS cases from VMAT to MBRT.
- MBRT plans utilized 6 MV photons and electron energies (6-20 MeV) on a Varian TrueBeam linac.
- Compared dose to clinical target volume (CTV), bone, and organs at risk (OARs) using Wilcoxon signed-rank test.
Main Results:
- MBRT eliminated the need for bolus in 10/22 patients due to higher electron entrance dose.
- Clinical target volume (CTV) coverage was equivalent: 97.9% (MBRT) vs. 98.1% (VMAT).
- MBRT significantly reduced dose to normal tissue (14.9%) and bone (8.2%) compared to VMAT.
Conclusions:
- MBRT provides significant sparing of organs at risk for STS patients with subcutaneous involvement.
- MBRT achieves this without sacrificing target coverage compared to VMAT.
- MBRT is a logistically feasible technique deliverable on conventional linacs with clear dosimetric benefits.
