Linac-based stereotactic radiosurgery for brain arteriovenous malformations

Most papers dealing with radiosurgery for cerebral arteriovenous malformations (AVMs) present the results of gamma-knife treatment, whereas linac radiosurgery is becoming increasingly popular. Moreover, there is still much uncertainty about the rationale of combined endovascular and radiosurgical treatment. The aims of this study were to evaluate obliteration and rebleeding rates, and to determine factors influencing obliteration and adverse effects after linac-based stereotactic radiosurgery for cerebral AVMs.

Records of 62 consecutive patients were analysed. Thirty-one had partial embolisation, five surgery, 29 had no prior treatment. The mean follow-up was 28.4 months. The mean volume treated was 11.7cm(3) and included embolised portions of AVMs. Actuarial obliteration rates and annual bleeding hazard rates after radiosurgery were calculated using Kaplan-Meier survival and life table analyses.

Actuarial obliteration rates after 1, 2 and 3 years of follow-up were 17, 36 and 40%, respectively. Prior embolisation did not influence the obliteration rate. In 77.3% of patients, obliteration occurred during the first 2 years of follow-up. Annual bleeding hazard rates after stereotactic radiosurgery were 3.4 and 1.1% during the first and second year of follow-up, respectively. Non-symptomatic imaging abnormalities were detected in 33.9% of patients after a median time of 8.8 months. The Spetzler-Martin grade, AVM score, radiation dose, volume and AVM nidus < 3cm significantly influenced the probability of obliteration. A dose less than 15Gy significantly reduced the probability of obliteration.

At least a 3 year follow-up is required to accurately assess the outcome. The best effects of the treatment are achieved for small (<3cm), low-grade lesions with a low AVM score. The bleeding risk after stereotactic radiosurgery gradually decreases.