Isotoxic radiosurgery planning for brain metastases

Area of Science:

• Radiation Oncology
• Neurosurgery
• Medical Physics

Background:

• Radionecrosis (RN) is a known complication of radiosurgery (RS) for brain metastases (BM).
• Previous studies linked RN to RS dose, lesion volume, and brain dose parameters like V10-14Gy.
• Optimizing RS dose is crucial for balancing tumor control and normal brain toxicity.

Purpose of the Study:

• To develop a knowledge-based, individualized method for estimating the optimal RS dose.
• To create a prediction model for brain toxicity parameters and optimal RS dose based on lesion characteristics.
• To provide a practical formula for personalized RS dose prescription.

Main Methods:

• A prediction model was derived using 30 historical RS plans for single BM (0.2-20.3cc).
• The model involved deriving formulas for V10-18Gy prediction and establishing relationships with prescription dose and lesion volume.
• Validation was performed on 65 new patients with 138 BM lesions treated with VMAT.

Main Results:

• A linear relationship was found between planning target volume (PTV) size and brain toxicity parameters (V10-18Gy).
• An individualized RS prescription dose formula was derived: PD=[V12Gy+0.96+(1.44×PTV)]/[0.12+(0.12×PTV)].
• High correlation (R²=0.991) was observed between predicted and actual V12Gy in the validation cohort.

Conclusions:

• A simple, effective formula is proposed for estimating optimal individual RS dose for BM.
• The formula accounts for lesion volume and normal brain toxicity parameters (V12Gy).
• This approach enables personalized RS dose selection to mitigate radionecrosis risk.