Radt-20. Stereotactic Radiosurgery for Recurrent Primary and Metastatic Central Nervous System Malignancies in the Pediatric Population

OBJECTIVE The safety and efficacy of stereotactic radiosurgery (SRS) are not well described for pediatric patients. This study presents disease control and toxicity outcomes after SRS for malignant CNS lesions in this population. METHODS A retrospective chart review was performed for 55 SRS treatments at a single institution from 37 pediatric patients with primary or metastatic CNS malignancies between 2000-2023. Analyses were performed with descriptive statistics, Kaplan-Meier, and proportional hazards modeling. RESULTS Twenty-seven patients were treated with SRS for focal recurrences of primary CNS malignancies and ten patients were treated for brain metastases. Median age at SRS was 12 years (range 4-21). Primary CNS histologies included ependymoma, glioma, meningioma, and medulloblastoma. 70% of patients had prior brain radiation. Most SRS treatments were single fraction (median 18 Gy, range 11-20) with median follow up of 33 months. The 3-year actuarial rates of intracranial progression-free survival (IC-PFS) and overall survival (OS) post SRS were 22.1% and 59.6% respectively. The 1-year actuarial rate of local control (LC) was 80%. 9 patients (24%) had no evidence of intracranial disease at median follow up of 37 months. 19 patients (51%) developed distant brain recurrence without local failure at a median of 8 months. LC, IC-PFS, and OS were independent of tumor histology or grade. Patients who received SRS to a single lesion had higher IC-PFS compared to those with 2-4 or ≥5 lesions (3-year IC-PFS 32.2%, 6.7%, and 0% respectively, p=0.005). All patients with subsequent CNS recurrence after SRS underwent salvage therapy. 2 patients developed CTCAE grade 3 toxicity related to radiation treatment effect. CONCLUSION SRS for malignant CNS lesions in the pediatric population provides effective local control with low toxicity risk. Although there remains high risk of distant CNS failures after SRS, all patients were able to receive additional salvage therapy including re-irradiation.