Repeated radiosurgery for incompletely obliterated arteriovenous malformations

Object. The goal of this study was to define treatment results of repeated arteriovenous malformation (AVM) radiosurgery, namely AVM obliteration and complications. Methods. The authors analyzed their experience with repeated AVM radiosurge ry performed in 41 patients for whom follow-up review lasted at least 2 yea rs. The median duration of follow up was 34 months (range 7-65 months) afte r repeated radiosurgery in this group. The residual nidus was located withi n the area of focus (in field) of the initial radiosurgery in 28 patients ( 68%). Initial doses to the margin varied from 12.5 to 20 Gy (median 18 Gy). During repeated treatment the dose to the margin varied from 12.5 to 20 Gy (median 17 Gy) and the retreated volumes ranged from 0.4 to 7 cm(3) (media n 2.1 cm(3)). Follow-up angiography performed at least 2 years postradiosurgery revealed complete AVM obliteration in 21 (70%) of 30 patients. The estimated overall 2-year obliteration rate, based on findings on magnetic resonance imaging (eight of 11 obliterated) and angiography (29 of 41 obliterated) was 71%. O bliteration rates correlated with margin doses (p = 0.0045) with a trend to ward higher rates in casts with in-field nidus persistence (p = 0.0637). Th e dose-response curve for AVM nidus obliteration was not significantly diff erent from that of the initial radiosurgery. In two patients (5%) intracran ial AVM hemorrhage developed within 125.9 risk years after repeated radiosu rgery (1.6% per patient year). Persistent symptomatic adverse radiation eff ects developed in two (5%) of 41 patients following repeated radiosurgery. Postradiosurgical imaging changes were identified in 11 (27%) of 41 patient s, which correlated with a 12-Gy volume from repeated surgery (p = 0.019). Conclusions. When necessary, repeated AVM radiosurgery achieves obliteratio n with an acceptable risk. Despite the effects of previous irradiation, rep eated radiosurgery required similar or slightly higher radiation doses to a chieve the same in-field obliteration rates as those needed to obliterate a n AVM that had not been treated by radiation previously.