2091 - Longitudinal Outcomes and Toxicity after CNS Stereotactic Radiosurgery in Pediatric and AYA Patients

Purpose/Objective(s): To evaluate late-onset treatment-related toxicities in pediatric and adolescent young adult (AYA) populations (age <40 years) who have undergone Gamma Knife (GK) stereotactic radiosurgery (SRS). We hypothesized that late-onset toxicity rates for pediatric and AYA patients treated with SRS for both malignant and non-malignant CNS tumors would be low compared to conventional radiation treatments.

Materials/Methods: All patients aged <40 years at the time of GK SRS at a single institution from 2005-2025 were identified. Local failure, early-onset (<5 years), and late-onset (≥5 years) toxicity were recorded. Fisher’s exact test was used to compare toxicities between tumor subtypes.

Results: We identified 84 patients who met the inclusion criteria, with 73% of patients having greater than 5 years of follow-up. Relevant patient demographics are described in Table 1. Malignant conditions were most commonly melanoma metastasis (n=5), breast cancer metastasis (n=3), ependymoma (n=3), glioblastoma (n=2), and oligoastrocytoma (n=2). The most common benign diagnoses included arteriovenous malformation (n=25), meningioma (n=11), schwannoma/acoustic neuroma (n=10), and pituitary adenoma (n=4). Twenty-three patients experienced early-onset toxicities, including edema (n=8), radionecrosis (n=5), seizure (n=3), hemorrhage (n=2), and headache (n=2); three of these patients had a toxicity that persisted in longitudinal follow-up. Two patients experienced late-onset toxicities: one had two seizures and headaches, and the other experienced worsening fatigue, cognitive decline, and difficulty maintaining employment. There was no significant difference in incidence of early and late-onset toxicity between malignant and benign histologies (OR 1.93 95% CI 0.73-5.07, p=0.21). Of 199 total lesions treated with GK, there were 23 local failures (11.6%). Sixteen patients underwent GK SRS reirradiation for local failure.

Conclusion: This robust analysis of late-onset pediatric and AYA patient outcomes following GK SRS demonstrates low rates of late-onset toxicity and comparable rates of early-onset toxicity and loss of local control to those reported in the literature. GK SRS remains a safe and effective treatment modality for well-selected benign and malignant CNS tumors in the pediatric and AYA population.

Table 1: