2621 - Robotic Radiosurgery for the Treatment of Pediatric Arteriovenous Malformations

T. Treechairusame^1,2, L. Kim³, J. S. Chiang⁴, Z. B. White II⁵, S. Jackson⁶, J. Quon⁷, S. S. Mehta⁸, G. Appelboom⁹, S. D. Chang¹⁰, S. G. Soltys⁶, R. Guzman¹¹, S. Cheshier¹², R. L. Dodd¹⁰, G. A. Grant¹³, M. S. B. Edwards¹⁴, and I. C. Gibbs⁶; ¹Division of Radiation Oncology, Department of Radiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand, ²Department of Radiation Oncology, Stanford University School of Medicine, Stanford, Palo Alto, CA, ³Stanford Department of Neurosurgery, Palo Alto, CA, ⁴Department of Radiation Oncology, Stanford Health Care, Stanford, CA, ⁵University of South Alabama, Mobile, AL, ⁶Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA, ⁷Division of Paediatric Neurosurgery, The Hospital for Sick Children, Toronto, ON, Canada, ⁸Stanford University, Palo Alto, CA, ⁹Department of Neurosurgery, NYU Grossman School of Medicine, New York, NY, ¹⁰Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA, ¹¹Departments of Neurosurgery and Biomedicine, University Hospital of Basel, Basel, Switzerland, ¹²Division of Pediatric Neurosurgery, Department of Neurosurgery, University of Utah School of Medicine, Salt Lake City, UT, ¹³Department of Neurosurgery, Duke University School of Medicine, Durham, NC, ¹⁴Division of Pediatric Neurosurgery, Lucile Packard Children’s Hospital, Palo Alto, CA

Purpose/Objective(s): Pediatric intracranial arteriovenous malformations (AVM) have a greater cumulative lifetime risk of rupture than adults. While obliteration after radiation occurs in a dose-dependent manner, increasing radiation doses also pose a higher risk of adverse radiation effects (ARE). Radiosurgery is effective in adults, but less is known about the efficacy and safety of robotic radiosurgery for pediatric intracranial AVMs. Materials/

Methods: We performed a retrospective review of consecutive pediatric patients with AVMs at a single institution with minimum follow-up of 1.75 years who underwent robotic radiosurgery between 2005 and 2021 with one of 3 radiosurgery dosing schedules: 1) single-stage unfractionated, 2) single-stage fractionated, 3) volumetrically multi-staged treatment. Cox proportional hazards regression models were performed to identify predictors of AREs and obliteration.
Results: 95 patients (age:1-21 years, M:F 50:45) with 100 intracranial AVMs were identified for analysis. Median follow-up time was 4.5 years (range 1.75-15.25 years). Forty-four (46.3%) patients presented with ruptured AVMs. The mean AVM volume was 10.0 cm³ ±11.88 (range: 0.11-71.86 cm³). Most had Spetzler-Martin grade III (36.2%) and IV (31.9%). The overall rate of total obliteration was 52.6% (78.8% in single-stage unfractionated, 24.2% in single-stage fractionated, and 10% in multi-staged treatment) with a median obliteration time of 3.25 years (2.8- 4.1 years). Partial obliteration was achieved in 23.2% (17.3% in single-stage unfractionated, 30.3% in single-stage fractionated, and 30% in multi-staged treatment). In the univariate analysis, higher obliteration rate was associated with small volume (hazard ratio;HR 0.876, 0.812 – 0.945) (P=0.001), lower Spetzler-Martin grade (HR 0.437, 0.320 – 0.597) (P= <0.001), and higher single-fraction equivalent dose (HR 1.160, 1.020 – 1.198) (P= 0.015), respectively.Pretreatment hemorrhages were found in 51 patients (59.6 % in unfractionated, 45.5 % in fractionated, and 50% in multi-staged treatment). Thirteen patients experienced hemorrhage in the post-treatment period (3.8% in unfractionated, 12% in fractionated, and 60% in staged treatment). AREs were found in 31.6% of patients, many of whom (50%) had deep subcortical lesions. Male gender and V12Gy correlated with AREs (HR 0.447, 0.199 – 1.004) (P=0.051) and (HR 1.020, 1.000 – 1.041) (P=0.053), respectively.
Conclusion: Single-fraction radiosurgery is very effective in treating smaller pediatric AVMs with obliteration rates of 79%. While single-stage fractionated treatment was less effective in achieving total obliteration (24%), this approach significantly reduced the posttreatment hemorrhage rate by at least half. Unfortunately, only 10% of AVMs in the multi-staged cohort were obliterated and post-treatment hemorrhage rates were not reduced. AVMs located in deeper cortical regions and those with higher Spetzler-Martin grade remain challenging.