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Developing a class solution for Prostate Stereotactic Ablative Body Radiotherapy (SABR) using Volumetric Modulated
Louise J Murray1, Vivian Cosgrove2, John Lilley2
1Department of Clinical Oncology, St. James's Institute of Oncology, Cancer Research UK Centre, St. James's University Hospital, Leeds, UK; University of Leeds, UK.
Summary
Single partial arc Volumetric Modulated Arc Therapy (VMAT) is optimal for prostate Stereotactic Ablative Radiotherapy (SABR). A 6mm planning target volume margin is feasible, meeting objectives and organ-at-risk constraints.
Area of Science:
- Radiation Oncology
- Medical Physics
Background:
- Prostate Stereotactic Ablative Radiotherapy (SABR) requires precise radiation delivery.
- Volumetric Modulated Arc Therapy (VMAT) is a common technique for complex radiotherapy plans.
Purpose of the Study:
- To determine the optimal VMAT technique for prostate SABR.
- To evaluate the impact of planning margins and seminal vesicle inclusion on treatment plans.
Main Methods:
- Comparison of four VMAT arc arrangements (1FA, 1PA, 2FA, 2PA) using seven datasets.
- Evaluation of 1PA plans with varying CTV-PTV margins (6mm, 8mm) and inclusion of the proximal seminal vesicle (SV).
- Treatment planning performed using Monaco 3.2 with the Elekta Agility MLC system.
Main Results:
- All arc arrangements produced highly conformal plans.
- Single partial arc (1PA) significantly reduced rectal dose compared to single full arc (1FA).
- 6mm CTV-PTV margins met all constraints; 8mm margins and SV inclusion required constraint relaxation and increased organ-at-risk doses.
Conclusions:
- Single partial arc (1PA) VMAT is the optimal technique for prostate SABR.
- 6mm CTV-PTV margins are feasible and consistent with daily image-guided radiotherapy (IGRT) for prostate SABR.
