SU-E-T-463: Biological-Based Optimization and VMAT is Unnecessary for Stereotactic Body Radiation Therapy

Area of Science:

• Radiation Oncology
• Medical Physics
• Cancer Treatment

Background:

• Intensity-Modulated Radiation Therapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT) are advanced radiation techniques.
• Biological-based optimization aims to improve treatment plans beyond standard dosimetric objectives.
• Stereotactic Body Radiation Therapy (SBRT) requires precise dose delivery for small target volumes.

Purpose of the Study:

• To evaluate the dosimetric benefit of biological-based optimization (generalized Equivalent Uniform Dose - gEUD) compared to conventional dose-volume (DV) optimization.
• To compare the dosimetric performance of fixed-beam IMRT and VMAT for SBRT planning.
• To assess if VMAT offers advantages over fixed-beam IMRT when using biological optimization.

Main Methods:

• Patients with lung, pancreas, spine, and brain cancers underwent treatment planning with fixed-beam IMRT and VMAT.
• Plans were optimized using both DV and gEUD objectives.
• A limited number of segments/beams were used to ensure low fluence modulation suitable for SBRT targets.

Main Results:

• No significant dosimetric differences were observed between fixed-beam IMRT and VMAT, regardless of the optimization method (DV or gEUD).
• gEUD optimization did not yield superior plans compared to DV optimization for SBRT cases.
• VMAT did not demonstrate a dosimetric advantage over fixed-beam IMRT, even with non-coplanar beams, for small SBRT targets.

Conclusions:

• Biological-based optimization (gEUD) does not provide a clear dosimetric benefit for fixed-beam IMRT or VMAT in SBRT.
• VMAT does not offer dosimetric advantages over fixed-beam IMRT for SBRT, with reduced treatment time being its primary benefit.
• The complexity of fluence modulation for small SBRT targets may limit the potential benefits of advanced optimization techniques.