Treatment of arteriovenous malformations (AVM) with linac stereotactic radiosurgery: A comparative study with large AVM

Introduction: Radiosurgery is a well known modality treatment in the management of AVM with a size diameter less or equal than 3 cm. Two years follow-up time is estimated to be necessary to evaluate the AVM response to treatment. Our purpose is to evaluate the efficacy of a lower single dose irradiation compared to the other authors (mean marginal dose of 1.387 cGy and maximum dose of 1.914 cGy to the smaller AVM, and mean marginal dose of 1.369 cGy and maximum dose of 2.400 cGy to the bigger AVM), during a follow-up time prolonged to 3 years. Methods: From August 1991 to August 1996, a total of 1.072 patients have been treated at our unit with radiosurgery using the University of Florida Radiosurgery System; and 409 of them were AVM of the brain: 361 are typical AVM. 208 of 361 AVM had a volume smaller than 14.000 mm3, and 66 had a volume bigger. A follow-up time between 12-60 months (mean: 29) has been considered. Results: The total occlusion rate to the smaller AVM was as follows: At 12 months, 46 out 179 AVM had a total occlusion: 26%. At 24 months, 75 out 112 AVM had a total occlusion: 67%. At 36 months, 39 out 43 AVM had a total occlusion: 91%. The total occlusion rate to the bigger AVM was as follows: At 12 months, 0 out 54 AVM had a total occlusion: 0%. At 24 months, 3 out 27 AVM had a total occlusion: 11%. At 36 months, 2 out 9 AVM had a total occlusion: 22%. Before the total AVM occlusion, 6 out 208 (2.8%) AVM evaluated smaller than 14.000 mm3 had a rebleeding episode (versus 4 out 66 [7.6%] AVM evaluated bigger than 14.000 mm3), and with a median follow-up of 29 months, the annual rebleeding estimated rate is 1.08% to the smaller AVM (3.1% to the bigger AVM). Seven patients had a mild neurological deficit related to radiosurgery procedure, and all of them were reversible at 3-6 months.