Frameless Stereotactic Radiosurgery (SRS) of Brain Arteriovenous Malformation (AVM); A Systematic Review, Meta-Analysis, and a Specific Analysis on Single-Session SRS.

BACKGROUND: Intracranial arteriovenous malformations (AVMs) are complex vascular lesions associated with hemorrhage, neurological morbidity, and mortality. This study evaluates the efficacy and safety of frameless stereotactic radiosurgery (SRS) for brain AVMs. METHODS: A comprehensive literature search was conducted across three databases through February 8, 2026. Primary outcomes included complete obliteration (CO), adverse radiation effects (AREs), and post-SRS hemorrhage. Pooled estimates included all extractable frameless SRS data, covering mixed-fraction cohorts. Analyses labeled as single-session referred to arms identified as single-fraction. Frame-based observations were only employed in one separate exploratory head-to-head comparison of two studies. RESULTS: Eleven publications from 2009 to 2024 were included, comprising 730 patients, although some outcomes were reported per AVM or treatment target. The pooled CO rate was 64% (95% CI, 59%-69%), the pooled ARE rate was 11% (95% CI, 3%-18%), and the pooled post-SRS hemorrhage rate was 3% (95% CI, 2%-5%). Mortality was rare (0.1%; 95% CI, 0.09%-0.11%), and persistent neurological deficits occurred in 17% (95% CI, 7%-27%). An inverse relationship was found between mean maximum dose and CO (P = 0.026, R2 = 100%) in an exploratory meta-regression of five studies. The frameless and frame-based SRS were found to be statistically similar in two observational comparative studies. CONCLUSION: The pooled CO rate for selected brain AVMs was 64%, and the hemorrhage rate after frameless SRS was low. Nonetheless, careful patient selection, treatment planning, and follow-up remain crucial. Currently, there is a lack of comparative evidence to establish equivalence with frame-based SRS.