Outcomes of Pediatric Patients with Intracranial Arteriovenous Malformation Treated With Proton Beam Stereotactic Radiosurgery

Abstract

Intracranial arteriovenous malformations (AVMs) pose a significant concern within the pediatric population given the projected life span of patients and the high cumulative risk of hemorrhage per year. The use of proton radiation allows for a conformal delivery of radiation dose that potentially minimizes the exposure of surrounding normal brain tissue to harmful treatment effects. The purpose of this study is to evaluate the response and toxicity rates of pediatric patients with intracranial AVMs treated at this institution with proton-based stereotactic radiosurgery (SRS).This IRB-approved single-institution study examines a cohort of 24 pediatric patients (≤ 18 years old) with 25 brain AVM lesions treated with proton radiosurgery between 2006 and 2018. Median age of patients was 14 years old, and median target volume was 8.14 cc. Lesions were treated to 20-25 Gy in 1 or 2 fractions, with 18 (72%) lesions receiving 25 Gy in 2 fractions. Per institutional guidelines, new lesions ≥5cc and lesions ≤15cc undergoing re-treatment received treatment in 2 fractions. Those in high-risk locations were also considered for 2-fraction treatment per physician discretion. Lesions were classified by Spetzler-Martin grading scale, ranging from grade 2 (24%), grade 3 (52%), and grade 4 (24%). There were no grade 1 or 5 lesions. 12 patients (48%) underwent prior surgery or embolization.Median follow-up time was 54 months. Of 25 treated lesions, 12 (48%) were found to have complete obliteration of nidus confirmed on angiogram, with first imaging showing obliteration at a median time of 38 months. Another 12 (48%) patients exhibited residual nidus on imaging with noticeable decrease in size. Of these patients, one was treated with a second course of proton-based SRS as an adult due to symptoms from the residual nidus. One (4%) patient had minimal decrease in lesion size on 3-year follow-up imaging with subsequent intracranial hemorrhage shortly afterwards, requiring resection and second course of radiosurgery at their local institution. All patients tolerated proton radiation treatment well without any toxicity noted, with the exception of one who experienced nonspecific intracranial edema requiring temporary steroid treatment. No patient deaths were observed at last follow-up.Stereotactic irradiation is often offered as a treatment option for intracranial AVMs given their high propensity to bleed, especially for those considered high risk for surgical intervention. While dose prescriptions do vary among published proton treatment experiences, this study shows the use of 20-25 Gy in one- to two-fractions to safely treat intracranial AVMs in pediatric patients while maintaining comparable efficacy rates.B.K. Lee: Employee; Amgen. L.N. Loredo: None. J.D. Slater: None.