Central Nervous System
PV QA 2 - Poster Viewing Q&A 2
Purpose/Objective(s): Potential dosimetric and clinico-pathologic predictors of radiation-induced brain edema after SRS for non-BOS meningiomas were analyzed.
Materials/Methods: We analyzed 26 studies (PubMed indexed from 1998-2017) that included all or some non-BOS meningioma patients, reported risks of edema after SRS, and correlated dosimetric and/or non-dosimetric measures with magnitude of risk. Studies with the following characteristics were excluded:
Results: Among 26 studies, factors reported to significantly correlate with increased risks of edema and/or symptomatic edema after SRS for meningioma include: greater tumor margin and/or maximum dose, greater tumor size and/or volume, non-BOS (particularly parasagittal) location, no prior resection for meningioma, and presence of pre-treatment edema. The extent and significance of these factors were inconsistent across studies. Among those 13 (of 26) studies that included only, or separately grouped, non-BOS meningomas, any new or progressive edema occurred in 28-50% and symptomatic edema occurred in 5-43% following SRS for non- BOS meningiomas. Among those with any new or progressive edema, symptomatic edema developed in 24-91% (among 7 studies that reported both outcomes). The average time to onset of edema ranged from 3-9 months in most studies. From data extracted from these 13 studies, other than a counter-intuitively lower risk of symptomatic edema with larger tumor volume, the regression curves were relatively flat (i.e. no discernable relationship) across the range of reported mean/median dose and volumes. The regression coefficients demonstrated poor correlations (i.e. values much lower than 1.0).
Conclusion: The variability in risks of edema and in factors impacting those risks are likely due to differences across studies in patient and tumor clinico-pathologic characteristics as well as in treatment modalities and SRS planning and delivery parameters. Potentially important dosimetric factors, such as volume of brain or tissue receiving single-fraction doses >10-12 Gy, are not well-studied. More studies on pooled populations, grouped by potential prognostic factors such as tumor location and prior therapy, are needed to better understand dosimetric and non-dosimetric factors predictive of edema risk after SRS for meningioma.
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