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Stereotactic Radiosurgery for Gynecologic Cancer
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Optimizing anisotropic margins in single-isocenter multiple brain metastases radiosurgery using regressor strategies:
José Alejandro Rojas-López1,2, Miguel Ángel Chesta1, Francisco Tamarit1,3,4
1Facultad de Matemática, Astronomía, Física y Computación, Universidad Nacional de Córdoba, Córdoba, Argentina.
Journal of Applied Clinical Medical Physics
|August 31, 2025
Summary
Anisotropic margins in single-isocenter multiple-metastasis radiosurgery (SRS) can reduce irradiated brain volume. While dosimetric benefits like improved gradient index and reduced V12 were observed, clinical impact may be modest.
Area of Science:
- Medical Physics
- Radiation Oncology
- Neurosurgery
Background:
- Single-isocenter multiple-metastasis radiosurgery (SRS) aims to deliver precise radiation doses to multiple brain lesions.
- Optimizing radiation margins is crucial to balance tumor coverage and minimize dose to surrounding healthy brain tissue.
- Current methods may not fully account for all factors influencing margin size, potentially leading to unnecessary irradiation.
Purpose of the Study:
- To develop and evaluate a comprehensive method for assigning anisotropic margins in single-isocenter multiple-metastasis SRS.
- To utilize regressor strategies incorporating geometric, dosimetric, and mechanical information for margin optimization.
- To assess if anisotropic margins can reduce irradiated brain volume without compromising lesion coverage.
Main Methods:
- Investigated slice thickness impact on margins using an anthropomorphic phantom.
- Assigned anisotropic margins using geometric margin criterion (GMC) and optimized margin criterion (OMC) based on regressor strategies in clinical cases.
- Evaluated treatment plans (456 metastases) using conformity, gradient, efficiency indices, monitor units, V12, and radiobiological models for radionecrosis risk.
Main Results:
- Optimized margin criterion (OMC) reduced target volumes by 20% and improved gradient index and monitor units compared to GMC.
- OMC resulted in a statistically significant decrease in V12 (5%-41%) across institutions.
- Radiobiological models indicated a low radionecrosis risk (<10%) with no significant difference between GMC and OMC.
Conclusions:
- Anisotropic margins show feasibility and potential dosimetric benefits in SRS, including improved gradient index and V12.
- The clinical impact of these dosimetric improvements may be modest.
- Anisotropic margins can be integrated into SRS workflows, offering advantages in minimizing brain dose in specific scenarios.
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