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Prognostic factors for complete obliteration of arteriovenous malformations treated with LINAC-based stereotactic radiosurgery
Tim J. Kruser, Wolfgang A. Tome, Songwon Seo, John S. Kuo, Patrick A. Turski, Richard J. Chappell, Rufus A. Scrimger, Minesh P. Mehta

Objectives: Few series analyzing prognostic factors predicting for obliteration of arteriovenous malformations (AVMs) following linear accelerator (LINAC)-based stereotactic radiosurgery (SRS) have been reported. We analyzed prognostic variables, outcomes, and toxicities in 88 patients undergoing LINAC-based SRS for AVMs.

Methods: Following IRB approval, patient records were retrospectively analyzed to identify independent predictors of complete response (obliteration) (CR) and time-to- CR. The majority of AVMs were treated using multiple isocenters and non-coplanar arcs. The median AVM volume was 2.67 cm3 (0.05 – 33.51). Median marginal and maximal doses were 17 (12-24) and 26.1 Gy (15- 40), with a median prescription isodose surface of 65%.

Results: Spetzler-Martin (SM) grade was determined for 86 patients and was: I–3 pts (3%); II–23 pts (27%); III–45 pts (52%); IV–13 pts (15%); V–2 pts (2%).Of 80 patients with follow-up imaging, 44 (55%) had documented complete responses (CR). Kaplan-Meier estimate probability for CR at 4 years was 62% (95% CI: 0.50, 0.74). Median time to CR was 3 years (95% CI: 2.08, 3.17). Multivariate analysis demonstrated the Spetzler-Martin grade (OR=0.14 for grade III vs. grade I-II; p=0.004 and OR 0.07 for grade IV-V vs. grade I-II; p=0.002) and dichotomized marginal dose > 17 Gy (OR=4.19; p=0.01) to be significantly associated with CR.

Discussion: This report demonstrates that for LINAC-based SRS of AVM, marginal dose and Spetzler-Martin grade are strong predictors of complete AVM obliteration

Keywords: LINAC radiosurgery, arteriovenous malformations, Spetzler-Martin grade, prognostic factors

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