Patterns of Failure After Linear Accelerator Radiosurgery for Cerebral Arteriovenous Malformations

Abstract Background Numerous studies have assessed the predictive factors of the arteriovenous malformation (AVM) response to stereotactic radiosurgery (SRS) but only a few have discussed the causes of failure. The aim of this study was to evaluate the patterns of failure in patients with AVM who had undergone LINAC SRS. Methods We performed a retrospective analysis of 288 patients treated by LINAC SRS in our institution from 1995 to 2011. Failure was defined on the basis of the control angiogram at 5 years and identified in 44 patients. The distribution of causes was estimated by a descriptive analysis of literature-based causes: minimal margin dose Results Incomplete nidus identification (41%) and prior embolization (77%) were the most frequently observed conditions in cases of failure. Previously embolized patients, in whom the cause of failure was always identified (p=0.001), were younger (p=0.004) and had larger nidus volumes (0.025). Recanalization was rare (5/34) and exclusively in females (p=0.048). Larger nidus volumes were less frequent (2.18 cm3 ±2.2 / [0.13-10.8]) and observed mainly in females when > 2 cm3 (p=0.012). Insufficient dose was observed in 9 patients and found in case of larger volume (p=0.031) leading to dosimetry constraints (3 cases) and vicinity of eloquent zones (6 cases). No known causes were found in 5 patients, 4 of whom had low Spetzler-Martin grades (I and II, p=0.003) suggestive of radioresistance. Conclusion Detailed analysis highlighted the distribution of causes and the potential role of radioresistance.