Effect of embolization before stereotactic radiosurgery for brain arteriovenous malformations: a case-control study with propensity score matching

The aim of this study was to evaluate whether endovascular embolization prior to stereotactic radiosurgery (SRS) has a negative impact on nidus obliteration for patients with arteriovenous malformations (AVMs). A total of 704 eligible patients with AVM who did not undergo prior surgery or radiotherapy were evaluated. Of these patients, 593 were treated with SRS only, and 111 were treated with embolization followed by SRS (E+SRS). Most patients in the E+SRS group (88%) underwent embolization with n-butyl-2-cyanoacrylate. In the comparison of radiosurgical outcomes between patients treated with SRS only and E+SRS, these groups were matched in a 1:1 ratio using propensity score matching to eliminate differences in basic characteristics. The primary outcome was to compare the nidus obliteration rates between the SRS-only and E+SRS groups. The secondary outcomes were the comparison of cumulative hemorrhage rates and the incidence of cyst formation or chronic encapsulated hematoma after SRS between these groups. In the unmatched cohorts, the actuarial 3-, 5-, and 8-year nidus obliteration rates after a single SRS session were 49.6%, 69.4%, and 74.1% in the SRS-only group, respectively, and 30.7%, 50.9%, and 68.6% in the E+SRS group, respectively (p = 0.001). In the matched cohort of 98 patients in each group, the rates were 47.1%, 62.0%, and 69.6% in the SRS-only group and 32.5%, 55.3%, and 75.0% in the E+SRS group, respectively (p = 0.24). There was no significant difference in either cumulative hemorrhage or the incidence of cyst formation or chronic encapsulated hematoma between the groups. Pre-SRS embolization did not affect nidus obliteration rates, cumulative hemorrhage rates, or the incidence of cyst formation or chronic encapsulated hematoma as late adverse radiation effects in patients with AVM treated with SRS.