Five year results of LINAC radiosurgery for arteriovenous malformations: Outcome for large AVMS

Purpose: For radiosurgery of large arteriovenous malformations (AVMs), the optimal relationship of dose and volume to obliteration, complications, and hemorrhage is not well defined. Multivariate analysis was performed to ass ess the relationship of multiple AVM and treatment factors to the outcome o f AVMs significantly larger than previously reported in the literature. Methods and Materials: 73 patients with intracranial AVMs underwent LINAC r adiosurgery. Over 50% of the AVMs were larger than 3 cm in diameter and the median and mean treatment volumes mere 8.4 cc and 15.3 cc, respectively (r ange 0.4-143.4 cc). Minimum AVM treatment doses varied between 1000-2200 cG y (median: 1600 cGy). Results: The obliteration rates for treatment volumes < 4 cc, 4-13.9 cc, an d greater than or equal to 14 cc were 67 %, 58 %, and 23 %, respectively. A VM obliteration was significantly associated with higher minimum treatment dose and negatively associated with a history of prior embolization with pa rticulate materials. No AVM receiving < 1400 cGy was obliterated. The incid ence of post-radiosurgical imaging abnormalities and clinical complications rose with increasing treatment volume. For treatment volumes > 14 cc recei ving greater than or equal to 1600 cGy, the incidence of postradiosurgical MRI T2 abnormalities was 72 % and the incidence of radiation necrosis requi ring resection was 22 %. The rate of post-radiosurgical hemorrhage was 2.7 % per person-year for AVMs;ls,vith treatment volumes < 14 cc and 7.5 % per person-year for AVMs greater than or equal to 14 cc, Conclusion: As AVM size increases, the dose-volume range for the optimal ba lance between successful obliteration and the risk of complications and pos t-radiosurgical hemorrhage narrows. (C) 1999 Elsevier Science Inc.