Two-Fraction Stereotactic Proton Therapy for Intracranial Arteriovenous Malformations

Abstract

Purpose/Objective(s): A collaborative approach to treating intracranial arteriovenous malformations is vital to successful management of large symptomatic arteriovenous malformations (AVM). Stereotactic proton therapy (SPT) acts as a key component, along with surgical resection and neurovascular embolization, attempting to decrease morbidity and mortality. This study aims to evaluate the obliteration rate, acute complications, and hemorrhage rate in patients treated with 2 fraction SPT for intracranial AVMs within a multimodal therapeutic approach. Materials/Methods: From 1993 to 2014, 124 patients were treated for intracranial AVMs with 2 fraction SPT as part of a multidisciplinary effort for treatment of these lesions as part of a registry trial. Asymptomatic patients were not treated. Patients presented with headache (n=59; 48%); seizure (n = 56; 45%); increasing neurologic deficit (n = 83; 67%); and hemorrhage (n = 61; 49%). Many patients had received prior treatment with embolization (n = 68; 55%), surgical resection (n = 26, 21%), or radiosurgery (n = 25; 20%). The median AVM nidus at time of SPT was 19.8 cc (range 0.3-191.2), with 52% in eloquent regions (Brainstem, Basal Ganglia/Thalamus, Motor Strip). The median prescription dose was 25 GyE (range 16-27.5 GyE). Follow up was done with MRI/MRA every 6-12 months and planned cerebral angiogram to confirm obliteration or after 3 years post SPT. Results: Of the 124 patients, 9 were lost to follow up, while the remaining 115 had a median follow-up of 92.9 months. Thirty-seven patients had additional therapy, some of which were planned, including embolization (n = 16), surgery (n = 18), or radiosurgery including additional SPT (n = 26). Of patients with at least 24 months follow up, the total obliteration rate was 30% (n=29) with a median time to obliteration of 39.7 months (range 14-196.2) and partial obliteration rate was 46% (n = 45) with median time of 22 months (range 4.5-137.3). The most common acute complications were headaches (n = 18; 16%); seizures (n = 11; 10%); and transient neurological deficits (n = 15; 13%). Twenty-four patients (21%) experienced post treatment hemorrhage with the median time to hemorrhage of 41.7mths (range 1.8-204.2). Ten patients (9%) died after treatment, with 9 of the patients dying after AVM hemorrhage and 1 from a primary tumor. Conclusion: The management of large, symptomatic, and/or eloquent AVMs requires the expertise and collaborative approach of the radiation oncologist, neurosurgeon, and neurointerventionalist. Two-fraction SPT is a key component in this multimodal approach, with this study showing effective obliteration while mitigating potential adverse effects.