Detailed evaluation of the long-term outcomes of repeat stereotactic radiosurgery for brain arteriovenous malformations: A single-center retrospective study.

Repeat stereotactic radiosurgery (SRS) is a treatment option for residual brain arteriovenous malformations (AVMs) following incomplete response to an initial SRS, and this study aimed to clarify the long-term outcomes. Patients who underwent repeat SRS between 1990 and 2022 were retrospectively analyzed. Primary outcome was a favorable patient outcome, defined as AVM obliteration without post-SRS hemorrhage or symptomatic T2 signal change/late radiation-induced complications (LRICs). Fifty-eight patients with a median follow-up of 97 months were analyzed. Six patients (10.3%) experienced recurrent hemorrhage between the initial and repeat SRS, indicating high risk of hemorrhage in this cohort. Favorable patient outcome was achieved in 41 patients (70.7%), with 3- and 5-year cumulative rates of 68.1% and 79.2%. Maximum dose was associated with a favorable patient outcome (hazard ratio [HR] 1.07, 95% confidence interval [CI] 1.01-1.14; p = 0.016). AVM obliteration was achieved in 47 patients (81.0%), with 3- and 5-year rates of 69.2% and 85.0%. Three patients (5.2%) experienced post-repeat SRS hemorrhage, with an annual hemorrhage rate of 1.66%/person-year. Five patients (8.6%) experienced LRICs requiring resection with 5- and 10-year rates of 4.0% and 6.9%. T2 signal change after initial SRS (HR 17.11, 95% CI 1.06-276.55; p = 0.046) and initial maximum diameter > 25 mm (HR 21.12, 95% CI 1.01-442.76; p = 0.049) were associated with LRICs. Repeat SRS demonstrated long-term favorable outcomes in patients at a high risk of hemorrhage. A longer follow-up duration is important, as in the case of LRICs, which could be predicted by T2 signal change and nidus size before repeat SRS.