The benefits and risks of pre–stereotactic radiosurgery (SRS) embolization have been reported in different studies. The goal of this study was to compare the long-term outcome of arteriovenous malformations (AVMs) treated with and without pre-SRS embolization.
A database including 1159 patients with AVMs who underwent SRS was reviewed. The embolized group was selected by including AVMs with pre-SRS embolization, maximal diameter > 30 mm, and estimated volume > 8 ml. The nonembolized group was defined as AVMs treated by SRS alone with matched de novo nidus volume. Outcomes including incidences of favorable clinical outcome (obliteration without hemorrhage, cyst formation, worsening, or new seizures), obliteration, adverse effects, and angioarchitectural complexity were evaluated.
The study cohort comprised 17 patients in the embolized group (median AVM volume 17.0 ml) and 35 patients in the nonembolized group (median AVM volume 13.1 ml). The rates of obliteration (embolized cohort: 33%, 44%, and 56%; nonembolized cohort: 32%, 47%, and 47% at 4, 6, and 10 years, respectively) and favorable outcome were comparable between the 2 groups. However, the embolized group had a significantly higher incidence of repeat SRS (41% vs 23%, p = 0.012) and total procedures (median number of procedures 4 vs 1, p < 0.001), even with a significantly higher margin dose delivered at the first SRS (23 Gy vs 17 Gy, p < 0.001). The median angioarchitectural complexity score was reduced from 7 to 5 after embolization. Collateral flow and neovascularization were more frequently observed in the embolized nonobliterated AVMs.
Both embolization plus SRS and SRS alone were effective therapies for moderately large (8–39 ml) AVMs. Even with a significantly higher prescription dose at the time of initial SRS, the embolized group still required more procedures to reach final obliteration. The presence of collateral flow and neovascularization could be risk factors for a failure to obliterate following treatment.