Ncog-27. long-term outcomes of gamma knife radiosurgery for growing meningioma

Abstract Gamma knife radiosurgery (GKRS) has become an effective treatment modality for intracranial meningioma. However, the role of GKRS in managing growing meinigoma during follow-up remains uncertain. This study aims to investigate the long-term outcome after GKRS treatment on meningioma for growing meningioma at follow-up. A retrospective analysis was conducted on patients who underwent GKRS as primary treatment for growing meingiomas between 2004 and 2021. Growing meningioma was defined as a >10% increase in volume compared to the previous imaging. Fifty-nine patients who received GKRS as initial treatment were included in this study with minimum follow-up period of 12 months. Patient clinical-radiological data, tumor characteristics and procedural details were analyzed. Tumor progression and regression were defined as a >10% increase or decrease in volume, respectively, compared to pre-GKRS image. Tumor volumes within ±10% of pre-GKRS volume were considered stable. At a median follow-up of 41 months (range 15-197 months), tumor volume was unchanged in 16 patients (27.1%), decreased in 41 patients (69.5%), and increased in 2 patients (3.4%). In multivariate analysis, growth rate was significantly associated with tumor progression (hazard ratio [HR]=2.059, 95% confidence interval [CI]=1.028-4.123, p=0.042). Eleven patients (18.6%) experienced new or worsening symptoms. In multivariate analysis, factors predicting new or worsening neurological function were preexisting symptoms (HR=7.159, 95% CI=1.468-34.911, p=0.015) and tumor calcification (HR=11.921, 95% CI=2.400-59.202), p=0.002), and pre-existing peritumoral edema (HR=9.751, 95% CI=1.666-57.058, p=0.012). GKRS demonstrates a high tumor control rate as well as an acceptable complication rate in growing meningioma. Effective tumor control is more likely in patients with slow-growing tumor.