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MO_10_2714 - Radiation-induced edema after single or multi-fraction stereotactic radiosurgery (SRS) for non-base of skull (non-BOS) meningioma: A pooled analysis

Monday, October 22
10:45 AM - 12:15 PM
Location: Innovation Hub, Exhibit Hall 3

Radiation-induced edema after single or multi-fraction stereotactic radiosurgery (SRS) for non-base of skull (non-BOS) meningioma: A pooled analysis
M. T. Milano1, M. Sharma1, S. G. Soltys2, A. Sahgal3, K. Y. Usuki4, J. M. Saenz5, J. Grimm6, and I. El Naqa7; 1University of Rochester Medical Center, Rochester, NY, 2Department of Radiation Oncology, Stanford Cancer Institute, Stanford, CA, 3Department of Radiation Oncology, Sunnybrook Odette Cancer Centre, University of Toronto, Toronto, ON, Canada, 4Department of Radiation Oncology, University of Rochester Medical Center, Rochester, NY, 5University of Rochester, School of Medicine, Rochester, NY, 6Johns Hopkins University, Baltimore, MD, 7Department of Radiation Oncology, University of Michigan, Ann Arbor, MI

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:

  • meningiomas limited to BOS, tentorium, posterior fossa, or optic sheath locations
  • patients limited to those with histologic grade 2-3 or multiple meningiomas
  • no data reported on tumor volume and/or target doses
  • risks of edema not reported
  • case reports
  • all patients analyzed in a subsequent update
From selected studies, linear, logarithmic and exponential regression analyses, weighted by patient number, were performed for risks of edema and symptomatic edema, relative to margin dose and relative to tumor/target size and volume.

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.

Author Disclosure: M.T. Milano: Honoraria; UpToDate. M. Sharma: None. S.G. Soltys: Honoraria; Inovio Pharmaceuticals. A. Sahgal: Research Grant; Elekta AB. Honoraria; Elekta AB, Varian. Travel Expenses; Elekta AB. Ex Officio; International Society of Stereotactic Radiosurgery. AO Spine Tumor Forum committee member; AO Spine. K.Y. Usuki: None. J. Saenz: None. J. Grimm: Research Grant; Accuray, NovoCure. developer and issued patent for software; DVH Evaluator. I. El Naqa: Research Grant; NIH.

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MO_10_2714 - Radiation-induced edema after single or multi-fraction stereotactic radiosurgery (SRS) for non-base of skull (non-BOS) meningioma: A pooled analysis



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