Background
Retrospective single-institution analysis (University of Pittsburgh). N=219 benign (WHO grade I) meningiomas treated with Gamma Knife SRS; all maximum diameter ≤35 mm. Analysis of risk factors for post-SRS complications by tumor location, dose, and volume.
Interventions and follow up
Treatment: Gamma Knife SRS (median margin dose 14 Gy) for benign meningioma ≤35 mm; complications analyzed by location, dose, and volume
Primary endpoint: Complication-free survival; predictors of post-SRS complications
mFollow up: Median 37 months
Primary endpoint: Complication-free survival; predictors of post-SRS complications
mFollow up: Median 37 months
Results
5-yr tumor control: 96.2%
Symptomatic post-SRS complication rate: 9.7% overall
Parasagittal/parafalcine complications: 16.5%
Cavernous sinus complications: 4.4%
Major complications (permanent deficit): 4.1%
Symptomatic post-SRS complication rate: 9.7% overall
Parasagittal/parafalcine complications: 16.5%
Cavernous sinus complications: 4.4%
Major complications (permanent deficit): 4.1%
Adverse events
New/worsening neurological deficit: 9.7%
Symptomatic peritumoral edema: 4.6%
Cranial neuropathy: 3.2%
Seizure: 2.3%
Risk factors: parasagittal location (16.5%) vs cavernous sinus (4.4%); tumor volume >7.5 cm³ associated with higher complication risk
Symptomatic peritumoral edema: 4.6%
Cranial neuropathy: 3.2%
Seizure: 2.3%
Risk factors: parasagittal location (16.5%) vs cavernous sinus (4.4%); tumor volume >7.5 cm³ associated with higher complication risk
Conclusions
SRS achieves 5-year local control of 96% for benign meningioma with acceptable overall complication rates of ~10%. Tumor location (parasagittal highest risk due to venous congestion) and volume (>7.5 cm³) are the key risk factors for complications, rather than dose alone.
Key Limitations
Retrospective, single-institution, no comparator arm. Relatively short median follow-up (37 months) limits late-complication and durable-control assessment. WHO grade I benign tumors ≤35 mm only — not generalizable to atypical/large meningiomas. Risk-factor associations are hypothesis-generating.
Clinical Context
Helped define modern SRS patient selection for benign meningioma — favoring smaller-volume, non-parasagittal tumors and informing dose/volume planning. Complements Pollock 2003 tumor-control data; together they support SRS as a standard option for small-to-medium grade I meningiomas.