Background: The annual bleeding risk for a brain arteriovenous malformation (AVM) is 2-8%, but obliterating the nidus reduces the risk to near population levels. We evaluate the outcomes of linear accelerator (LINAC)-based stereotactic radiosurgery (SRS) in the treatment of brain AVMs in our institutional cohort.
Methods: The study comprises patients treated with SRS for AVMs with follow-up care greater than one month from 2014-2021. Baseline characteristics were compared between pediatric and adults in the sample. Time-to-event analyses were conducted using the Kaplan-Meier survival method. Statistical significance is defined as P<0.05; all tests were two-tailed; no adjustments were made for multiple comparisons. Influences of baseline characteristics were evaluated using simple or multiple logistic regression.
Results: Among 29 qualifying patients with SRS-treated AVMs, a mean nidus volume of 6.26cm3 (SD=9.12, Range=0.13-40.2) and nidus max diameter of 24.8mm (SD=15.9, Range=2- 60) were observed. The distribution of Spetzler-Martin (SM) grades were SM1 (3.3%), SM2 (23.3%), SM3 (50%), SM4 (16.7%) and SM5 (6.7%). Pretreatment included intervention for hemorrhage (65.5%), embolization (43.3%), and microsurgery (13.3%). SRS for the AVM involved VMAT approach (50%), conformal arc (36.7%) and step-and-shoot IMRT (10%). The mean target dose was 18.72Gy (SD=1.7, Range=13.5-22) and delivered primarily in one fraction (86.7%). Obliteration occurred in 53.3% of patients and median time to obliteration was 27.1 months. Mortality was 10.3% with only one-cause specific death (AVM hemorrhage). Median follow-up was 23.6 months (Range=3-50.7). Comparing adult and pediatric patients, significant factors affecting likelihood of SRS delivery were sex (p=0.05), race (p=0.0089), nidus max diameter (p=0.033), pre-treatment SRS (p=0.027) and neurological deficits at presentation (p=0.0169). Likelihood of obliteration decreased with increasing nidus volume with an estimated 10% for each additional cm3 (OR=0.90, 95% CI=0.82-0.99, p=0.027). Adverse Events (AE) were observed in 55.2% of patients with a median time to AE of 11.4 months. Nidus max diameter significantly affected rate of AE (HR=1.36, 95% CI=1.03-1.8, p=0.031).
Conclusion: SRS resulted in 53.3% of our cohort achieving obliteration (mean follow-up: 23.6mos). Adverse events occurred in 55.2% of patients, but most were mild and resolved. Pediatric patients obliterate at similar rates to their adult counterparts but on an accelerated time course.

Institutional Experience of Linear Accelerator-Based Stereotactic Radiosurgery For Brain Arteriovenous Malformations 


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