2710 - Long-Term Complete Response Rates of Arteriovenous Malformations Treated with LINAC-Based Stereotactic Radiosurgery

H. Menon¹, T. Kruser², Z. E. Labby³, R. A. B. Bayliss³, W. A. Tome⁴, D. Jacqmin³, A. C. Arnold³, P. M. Hill³, A. S. Ahmed⁵, B. Aagaard-Kienitz⁵, D. Niemann⁵, R. J. Demsey⁵, S. P. Howard³, and B. A. Morris³; ¹Department of Human Oncology, University of Wisconsin Hospitals and Clinics, Madison, WI, ²SSM Health Dean Medical Group, Turville Bay Radiation Oncology Center, Madison, WI, ³Department of Human Oncology, University of Wisconsin Carbone Cancer Center, Madison, WI, ⁴Department of Radiation Oncology, Montefiore Medical Center, Bronx, NY, ⁵Department of Neurological Surgery, University of Wisconsin Hospital and Clinics, Madison, WI

Purpose/Objective(s): Treatment of arteriovenous malformations (AVM) with stereotactic radiosurgery (SRS) has been shown to lead to complete response in short-interval time series. The long-term outcomes for these patients has remained a clinical question. Here we present the long-term outcomes of LINAC-based SRS treatments at a high-volume single institution academic center. Materials/

Methods: Consecutive patients treated with LINAC-based SRS treatments with a diagnosis of AVM between 1989-2023 were identified. Clinical and dosimetric data were retrospectively collected. Kaplan Meier analysis was utilized to calculate time to complete response (CR). Multivariate linear regression was performed to identify prognostics indicators for disease response.

Results: One-hundred and forty patients were identified. Seven patients did not have adequate follow-up imaging to assess disease response, leaving 133 patients evaluable for this study. 70 patients had a reported CR to SRS treatment. An additional 48 patients had a partial response (PR), 11 had stable disease (SD), and 4 had progressive disease (PD). The Kaplan Meier plot estimate probability for CR at 10 years was 56.5% (95% CI: 0.47, 0.68). Median Kaplan Meier estimate of CR achievement was 13.2 years. Of the patients who did not achieve CR (n= 63), median follow-up imaging was 7.2 years. 19 patients (14%) of patients did experience a bleed after SRS treatment, with median time reported of 30 months. Multivariate analysis demonstrated the Spetzler-Martin grade (p=0.01), treatment dose (p=0.009) and target volume (p=0.026) were significantly associated with CR rates.

Conclusion: LINAC-based stereotactic radiosurgery in the setting of arteriovenous malformations appears to maintain long-term efficacy and safety. Spetzler-Martin grade, dose and treatment volumes are strong predictors for long-term efficacy of SRS for CR in these patients.