Background: Single-fraction radiosurgery may carry a higher risk of symptomatic peritumoural edema than conventionally fractionated radiotherapy, with a reported incidence of 2.5-37%. Previous research has shown that larger tumor volume and margin dose >14 Gy are associated with increased risk of toxicity. Parasagittal location has been associated with toxicity in some studies, but not in others.
Objective: To determine risk factors for and patterns of post-radiosurgical symptoms (PRS).
Methods: This single-institution retrospective chart review included 282 stereotactic radiosurgery (SRS) procedures for an intracranial meningioma from 1/1999-3/2011. PRS were assessed using the Common Terminology Criteria for Adverse Events (CTCAE, Version 4.0). Statistical analyses were conducted using the 194 procedures for which treatment plans were available.
Results: PRS were observed after sixty-five procedures (23%); 35 (12%) were grade 2 or higher. Post-treatment edema occurred in 21% of grade I PRS, 68% of grade II PRS, and 71% of grade III PRS. Tumor volume >=7.1 cc (adjusted hazards ratio=4.9, p=0.02), prior external beam radiotherapy (adjusted hazards ratio=2.6, p=0.03), and histologic grade (p=0.0052) predicted PRS. On multivariate analysis, parasagittal location was not predictive of PRS, though skull base location predicted a lower risk of symptomatic post-treatment edema (adjusted hazards ratio=0.133, p=0.02).
Conclusion: In our series, prior external beam radiotherapy, tumor volume, and tumor grade are risk factors for PRS, while pre-treatment edema approached statistical significance. Peritumoural edema is the predominant mechanism of significant PRS and skull base tumors have a lower risk of post-treatment edema.
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