2067 - Reporting Long-Term Clinical Outcomes of Radiosurgery Treatment for Intracranial Arteriovenous Malformations: A Single Institutional Retrospective Study

Purpose/Objective(s): Stereotactic radiosurgery (SRS) for intracranial arteriovenous malformations (AVM) and arteriovenous fistulas (AVF) is the gold standard treatment via same-day radiosurgery. Herein, we present our long-term clinical follow up outcomes in patients with AVM and AVF treated via the stereotactic radiosurgery system.

Materials/Methods: In this IRB approved single-institutional retrospective study, a total of 112 patients who underwent GK SRS treatment to their AVM or AVF anomalies between 2010 and 2024 were selected. Utilizing contrast-enhanced angiograms for nidus size delineation, highly conformal SRS plans were generated either manually or via lightening dose optimizer on high-resolution MRI images. Average target size was 7.6+/-13.6 (0.2–68.3) cc. Mean marginal prescription dose to nidus was 19.3+/-2.6 (14.0–24.0) Gy, prescribed to 50% isodose line. GK SRS plans were evaluated for Paddick conformity and gradient indices (PCI, GI), maximum dose to brainstem and optic pathway and normal brain receiving V_8Gy, V_10Gy, V_12Gy, and V_14Gy. Patient reported treatment response and toxicity profiles were obtained from clinical follow-up outcome reports in 6-month intervals.

Results: For highly conformal AVM and AVF GK-SRS plans, PCI and GI were 0.63+/-0.11 (0.38–0.86) and 2.8+/-0.3 (2.4–3.5), respectively. Average maximum dose to brainstem and optic pathway were 5.0 Gy (maximum, 16.1 Gy) and 1.5 Gy (maximum, 7.9 Gy). Normal brain receiving V_8Gy, V_10Gy, V_12Gy, and V_14Gy were 18.7, 12.1, 8.1 and 5.3 cc, on average. 70 of 112 patients had clinical outcome with mean follow up intervals of 63±49 (6–183) months. Their median age was 45±17 (7–83) years; 36 (51.4%) were female and 34 (48.6%) male. Of these 57 (81.4%) were treated for AVM per Spetzler-Martin (SM) AVM grading I-V; 11 (15.7%) treated for AVF and 2 (2.6%) treated for both anomalies. Total, 54 (77.1%) patients responded symptomatically to GK SRS, while 16 (22.9%) with higher SM grade AVM and larger nidus size did not. Patient follow-up showed normal brain radionecrosis in 11 (15.5%) AVM patients (4 of them were staged AVM, SM grade IV-V) and brainstem toxicity and optic pathway toxicity reported each in 1 (1.4%) patient. No AVF patients reported any adverse effect. 10 (91%) of those 11 AVM patients who presented with brain radionecrosis were female with relatively larger nidus (8.2–41.5 cc) and 5 of them didn’t respond to GK SRS. This subgroup had relatively higher V_12Gy of 11.8 cc, maximum up to 24.3 cc. They were managed by steroids, pentoxifylline, Vitamin E or intra-arterial bevacizumab for their radionecrosis.

Conclusion: Our long-term clinical follow up results of both AVM and AVF anomalies treated via same-day GK SRS is a highly effective treatment with less radiation induced adverse effect. However, AVM patients who developed brain radionecrosis were more often female patients with larger nidus size with higher SM grade. These clinical findings can be used to further minimize normal brain dose to future female patients with larger AVM.