1306. Gamma Knife Radiosurgery (GKRS) for Treatment of Arteriovenous Malformations in the Pediatric Population: A Single Institution Experience

Authors: Nathan Oh, DO; Nathan Oh, DO; Darcy Engelhart, BS; Joffre Olaya, MD; William Loudon, MD (Orange, CA)

Introduction: Studies pertaining to the efficacy and methods for treatment of arteriovenous malformations in the pediatric population remain limited despite large studies in the adult population. The prescription dose, size of the AVM and technical nuances of targeting and planning have resulted in a wide variance of published results. Furthermore, no standardized method for treating pediatric AVMs currently exists.

 Methods: A retrospective analysis was performed at a single-institution and data was obtained from 20 pediatric patients (<18 years of age). Each patient was treated with Gamma Knife Radiosurgery, directed at the AVM nidus between 2007 and 2018. The median prescription dose prescribed was 23 Gy (range 21-25Gy). Mean dose of 22.85Gy.  Each patient underwent follow-up with Diagnostic cerebral angiogram or CT- Angiography at 3-6 month intervals.

 Results: The AVM obliteration rate at 24 months after primary GKRS was 71.4%. The mean time to occlusion was 13.5 months. 3 patients were lost to follow-up (15%). The mean volume treated was 1.88cm3 (range 1.83cm-4cm). No complications were noted after treatment. Mean follow-up time was 52.7 months (4.39 years).

Conclusions: Gamma Knife Radiosurgery (GKRS) is an effective and safe treatment alternative for pediatric AVMs. The majority of pediatric studies have demonstrated greater >50% occlusion rate at a median time point of 40 months (3.3 years) and prescription dose <20 Gy, during which the risk of re-hemorrhage has been noted to range from 4-15% when  the AVM is not completely obliterated.  Here we show that dose escalation to >20 Gy (median dose of 23Gy in our study) has resulted in quicker obliteration rates (71.4% at 24 months) with mean time to occlusion at 13.5 months and 0% post-treatment hemorrhage rate. This study elucidates the utility of dose escalation for the treatment of pediatric AVMs using Gamma Knife Radiosurgery