Disparity of volumetric and linear measurements of meningioma response to gammaknife radiosurgery

Abstract

Objective: To identify clinical, radiological, and dosimetric predictors of meningioma response to stereotactic radiosurgery (SRS), and post-SRS adverse radiation events (ARE). Methodology: A retrospective review was conducted. Seventy-five patients had at least 24 months of clinical and radiological follow-up. Tumor control was defined as any volumetric/diametric change less than +10%. Volumetric measurements were made using T1-Gadolinium enhanced 3T MRI scans with ITK-SNAP2.2 software. Univariate statistics were used to identify predictors of post SRS AREs. Results: Females comprised 69.3% of patients, mean treatment age was 58.6 years, and median follow up was 36.2 months. Twenty-one patients had undergone prior surgical resection. Volumetric tumor control (52%) was inferior to diametric control (92%). Twenty-six patients (34.6%) experienced some form of new-onset complication after SRS: Headache (17.3%), cranial neuropathy (10.6%), speech impairment (2.7%), tremor (2.7%), and ataxia (1.3%). Fourteen patients (18.7%) experienced new onset T2 signal change signifying of edema; eight of these patients were symptomatic. Lower Conformity index (1.24 vs. 1.4), and higher treatment-volume ratio (TVR) (0.80 vs. 0.72) were significantly associated with development of edema after SRS (p<0.05, power > 0.8). Conclusion: Volume-based reporting of SRS outcomes for meningiomas is more accurate for reporting tumor control. Conformity index and TVR were identified as predictors of edema following radiosurgery.