Stereotactic radiotherapy for AVMs: the University of Toronto experience

Since July 1989, 66 patients have received stereotactic radiosurgery for arteriovenous malformations of the brain. All cases were reviewed by our multidisciplinary group. As result of our treatment algorithms these patients underwent stereotactic radiosurgery, either as the sole therapy or as part of combined modality treatment. Using a 6 MV linear accelerator, we have usually employed doses of either 15 or 20 Gy to the edge of the lesion, ensuring that critical normal structures do not receive a dose in excess of 15 Gy. Of the initial 24 patients followed for a minimum of 2 years, 12 have complete obliteration documented by angiography; 8 have > 90% obliteration (several have deferred further angiographic follow-up which may show progression to complete obliteration); 3 have had the nidus diminish; and one has had no change. Within this cohort, one patient experienced a transient acute effect; one patient has developed a minor late effect; one suffered a fatal hemorrhage despite ongoing response to radiosurgery; one has recently undergone retreatment.