LINAC stereotactic radiosurgery for brain arteriovenous malformations: An updated single centre analysis of outcomes

Arteriovenous malformations (AVM) of the brain are congenital, high pressure vascular malformations, which are at risk of haemorrhage. Stereotactic radiosurgery (SRS) can obliterate the nidus by delivering a precise high dose of ionising radiation in a single fraction. This paper updates long term AVM obliteration rates, time to obliteration and retreatment outcomes in LINAC delivered SRS treatment at the Royal Adelaide Hospital. A retrospective review of a prospectively maintained AVM SRS database supplemented by clinical case notes, patient correspondence and electronic medical records was performed. 89 AVMs received primary SRS treatment for which the crude obliteration rate was 61% (68% for 79 patients with adequate follow up). Higher marginal dose, smaller nidus size and lower Pollock-Flickinger (PF) score were significantly associated with AVM obliteration. The crude obliteration rates for patients with adequate follow-up and AVM diameter < 3 cm vs ≥ 3 cm were 76% vs 48%, respectively, and 93% with PF score < 1.0. Median time to obliteration was 36 months. Higher dose and lower PF score were associated with earlier obliteration. The crude obliteration rate after second SRS was 56% (9/16 patients) and no significant associations were found. These obliteration rates after primary and retreatment LINAC SRS are comparable to other studies. Marginal dose and PF score were the main predictors of obliteration overall as well as early (<36 months) obliteration.