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Updated: Jun 2, 2026
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Stereotactic Radiosurgery for Gynecologic Cancer
Published on: April 17, 2012
Minimization of Geometric Uncertainties and Setup Errors Improves Tumor Control for Intracranial Stereotactic
Tenyoh Suzuki1,2, Hidenobu Tachibana1, Yuta Takahashi3
1Section of Radiation Safety and Quality Assurance, National Cancer Center Hospital East, Chiba, Japan.
Advances in Radiation Oncology
|June 1, 2026
Summary
Geometric uncertainty in stereotactic radiosurgery (SRS) significantly impacts larger brain metastases tumor control probability (TCP). Tailoring treatment margins to tumor size may improve outcomes in SRS.
Area of Science:
- Radiation Oncology
- Neurosurgery
- Medical Physics
Background:
- Stereotactic radiosurgery (SRS) is a key treatment for brain metastases.
- Geometric uncertainty can affect treatment precision and tumor control probability (TCP).
- Current SRS protocols often use uniform planning target volume (PTV) margins.
Purpose of the Study:
- To evaluate the impact of 1-2 mm geometric uncertainty on TCP in brain metastasis SRS.
- To assess if tumor size influences the effect of geometric uncertainty on TCP.
- To inform personalized PTV margin strategies in SRS.
Main Methods:
- Retrospective analysis of 75 brain metastases in 50 patients treated with SRS.
- Simulation of geometric uncertainty by applying positional shifts to treatment plans.
- Comparison of dosimetric and radiobiological characteristics between small (≤20 mm) and large (>20 mm) tumors.
Main Results:
- Tumor size significantly modulated the effect of geometric uncertainty.
- Larger tumors (>20 mm) experienced a greater TCP reduction (median 10.9%) compared to smaller tumors (median 3.4%) with a 2 mm shift.
- Smaller tumors had steeper dose gradients but higher initial TCP, resulting in a modest absolute TCP decrease.
Conclusions:
- Larger brain metastases (>20 mm) are more vulnerable to TCP loss due to geometric uncertainties in SRS.
- Personalized treatment strategies, considering tumor size and radiobiological factors, are warranted.
- Future research should validate these findings and explore fractionated stereotactic radiation therapy.
