OBJECTIVE: Patients with deep-seated arteriovenous malformations (AVMs) have a higher rate of unfavorable outcome and lower rate of nidus obliteration after primary stereotactic radiosurgery (SRS). The aim of this study was to evaluate and quantify the effect of AVM location on repeat SRS outcomes. METHODS: This retrospective, multicenter study involved 505 AVM patients managed with repeat, single-session SRS. The endpoints were nidus obliteration, hemorrhage in the latency period, radiation-induced changes (RICs), and favorable outcome. Patients were split on the basis of AVM location into the deep (brainstem, basal ganglia, thalamus, deep cerebellum, and corpus callosum) and superficial cohorts. The cohorts were matched 1:1 on the basis of the covariate balancing score for volume, eloquence of location, and prescription dose. RESULTS: After matching, 149 patients remained in each cohort. The 5-year cumulative probability rates for favorable outcome (probability difference -18%, 95% CI -30.9 to -5.8%, p = 0.004) and AVM obliteration (probability difference -18%, 95% CI -30.1% to -6.4%, p = 0.007) were significantly lower in the deep AVM cohort. No significant differences were observed in the 5-year cumulative probability rates for hemorrhage (probability difference 3%, 95% CI -2.4% to 8.5%, p = 0.28) or RICs (probability difference 1%, 95% CI -10.6% to 11.7%, p = 0.92). The median time to delayed cyst formation was longer with deep-seated AVMs (deep 62 months vs superficial 12 months, p = 0.047). CONCLUSIONS: AVMs located in deep regions had significantly lower favorable outcomes and obliteration rates compared with superficial lesions after repeat SRS. Although the rates of hemorrhage in the latency period and RICs in the two cohorts were comparable, delayed cyst formation occurred later in patients with deep-seated AVMs.

Clinical Oncology Department Ain Shams University Cairo Egypt

Department of Neurological Surgery Hospices Civils de Lyon France

Department of Neurological Surgery University of Pittsburgh Pennsylvania

Department of Neurological Surgery University of Virginia Charlottesville Virginia

Department of Neurosurgery Koç University School of Medicine Istanbul Turkey

Department of Neurosurgery Neurological Institute Taipei Veteran General Hospital Taipei Taiwan

Department of Neurosurgery NYU Langone New York New York

Department of Neurosurgery Penn State Milton S Hershey Medical Center Hershey Pennsylvania

Department of Neurosurgery Postgraduate Institute of Medical Education and Research Chandigarh India

Department of Neurosurgery University of Sherbrooke CHUS Research Center Sherbrooke Canada

Department of Neurosurgery University of Southern California Los Angeles California; and

Department of Radiation Oncology The James Comprehensive Cancer Center Ohio State University Columbus Ohio

Department of Stereotactic and Radiation Neurosurgery Na Homolce Hospital Prague Czech Republic

Departments of19Neurosurgery and

Gamma Knife Center Cairo Nasser Institute Hospital Cairo Egypt

Neurosurgery Department and

Neurosurgery Department Benha University Qalubya Egypt

Radiation Oncology Department National Cancer Institute Cairo University Cairo Egypt

Radiation Oncology West Virginia University Morgantown West Virginia

Radiosurgery Unit Hospital Ruber Internacional Madrid Spain

School of Medicine National Yang Ming Chiao Tung University Taipei Taiwan

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