Robotic radiosurgery for the treatment of pediatric arteriovenous malformations

Pediatric intracranial arteriovenous malformations (AVMs) have a greater cumulative lifetime risk of rupture than those in adults. Although obliteration after radiation occurs in a dose-dependent manner, increasing radiation doses must be balanced against the risk of adverse radiation effects (AREs). The authors aimed to assess the efficacy of robotic radiosurgery for pediatric AVMs.

The authors performed a retrospective review of pediatric patients with AVMs at a single institution who underwent robotic radiosurgery between 2005 and 2021 with one of 3 radiosurgery dosing schedules: 1) single-stage unfractionated (SSU), 2) single-stage fractionated (SSF), and 3) volumetrically multistaged (VMS) treatment. Cox proportional hazards regression was performed to identify predictors of AREs and obliteration.

Ninety-five patients with 100 intracranial AVMs were identified. Median (range) follow-up time was 4.5 (1.8-15.2) years. Forty-four (46.3%) presented with ruptured AVMs. The mean ± SD AVM volume was 10.0 ± 11.88 cm3. A plurality of AVMs were Spetzler-Martin grade III (36.2%). The overall rate of total obliteration was 52.6% (78.8% of SSU-treated, 24.2% of SSF-treated, 10% of VMS-treated patients) with a median (range) obliteration time of 3.25 (2.8-4.1) years. Partial obliteration was achieved in 23.2% of patients. In the univariate analysis, the higher obliteration rate was associated with small volume (HR 0.876, 95% CI 0.812-0.945) (p = 0.001), no prior embolization (HR 0.472, 95% CI 0.254-0.876) (p = 0.017), lower Spetzler-Martin grade (HR 0.437, 95% CI 0.320-0.597) (p ≤ 0.001), and higher single-fraction equivalent dose (HR 1.160, 95% CI 1.020-1.198) (p = 0.015). Pretreatment hemorrhage was found in 51 patients (59.6% of SSU-treated, 45.5% of SSF-treated, and 50% of VMS-treated patients). Thirteen patients experienced posttreatment hemorrhage (3.8% of SSU-treated, 12% of SSF-treated, and 60% of VMS-treated patients). AREs were found afterward in 31.6% of patients. The correlations of male sex (HR 0.447, 95% CI 0.199-1.004) (p = 0.051) and volume of brain tissue that received a single-fraction equivalent dose of 12 Gy or greater (HR 1.020, 95% CI 1.000-1.041) (p = 0.053) with AREs did not reach significance.

SSU treatment was effective for treating smaller AVMs with an obliteration rate of 79%. Although SSF treatment was less effective in achieving total obliteration (24%), this approach significantly reduced the posttreatment hemorrhage rate by nearly 75% (46% of patients had pretreatment hemorrhage vs 12% with posttreatment hemorrhage). Unfortunately, only 10% of AVMs in the VMS cohort were obliterated and posttreatment hemorrhage rates were not reduced.