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Risk of hemorrhage and obliteration rates of LINAC-based radiosurgery for cerebral arteriovenous malformations treated after prior partial embolization.

Zabel-du Bois A, Milker-Zabel S, Huber P, Schlegel W, Debus J

Department of RadioOncology, University of Heidelberg, 69120 Heidelberg, Germany. A.Zabel@dkfz-heidelberg.de

PURPOSE: We investigate patient outcome, risk of hemorrhage, and factors affecting obliteration after LINAC-based radiosurgery (RS) for cerebral arteriovenous malformations (AVM) treated after partial embolization. METHODS AND MATERIALS: This analysis is based on 50 patients treated after prior embolization. According to the Spetzler-Martin criteria the AVM classification was as follows: 9 patients, Grade I (18%); 19, Grade II (38%); 18, Grade III (36%); and 4, Grade IV (8%). Median RS-based AVM score was 1.41. Median single dose was 18 Gy/ 80% isodose (range, 15-22 Gy) and median AVM volume was 4.0 cc (range, 0.2-22.6 cc). In all, 34 patients (68%) experienced hemorrhage before RS. Median follow-up was 3.1 year (range, 8.5 months to 15 years). RESULTS: Actuarial complete obliteration rate was 67% after 3 years and 78% after 4 years. The complete obliteration rate was significantly higher in AVM <3 cm (92% vs. 60%, p < 0.01) and in AVM Spetzler-Martin Grade I/II (90% vs. 59%, p < 0,01). Intracranial hemorrhage after RS was seen in 6 patients (12%) after 8.5 months median. Annual bleeding risk was 7.9% after 1 year and 2.2% after 2 years. It was found that AVM diameter > or =3 cm (p < 0.006), AVM volume > or =4 cc (p < 0.01), AVM score > or =1.5 (p < 0.03), and single dose <18 Gy (p < 0.03) were associated with a significant higher bleeding risk. CONCLUSIONS: The rate of obliteration after RS in AVM treated after prior partial embolization depends on size as well as Spetzler-Martin grade. The risk of intracranial hemorrhage is not increased after RS and depends on AVM score, size, and volume, as well as on applied single dose.

Published 19 July 2007 in Int J Radiat Oncol Biol Phys, 68(4): 999-1003.
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