RONC-18 Radiosurgery for Primary and Metastatic CNS Malignancies in the Pediatric Population

Abstract PURPOSE: The purpose of this study is to describe outcomes after pediatric radiosurgery for malignant CNS lesions. METHODS: Retrospective chart review was performed for 31 pediatric patients treated at a single institution with Gamma Knife stereotactic radiosurgery (SRS) for primary or metastatic CNS malignancies between 2000-2020. RESULTS: 25 patients were treated with SRS for focal recurrences of primary CNS malignancies, 1 patient was treated in the adjuvant setting after initial resection, and 5 patients were treated for brain metastases. Primary CNS histologies included ependymoma (n=14), glioma (n=4), medulloblastoma (n=2), and meningioma (n=2). 65% were WHO grade 3 or 4. 71% of patients had received a prior course of involved-field external beam radiation to the brain to a median dose of 59.4 Gy in 33 fractions. Median age at SRS was 14 years (range 4-21). Radiosurgery was predominantly performed in a single fraction to a median dose of 17 Gy to a total of 42 targets among 29 patients. Two patients underwent fractionated radiosurgery to 30 Gy in 5 fractions for larger lesions. Median follow up after SRS was 44 months. 7 patients (23%) had no evidence of disease after SRS at a median follow up of 39 months. 6 patients (19%) developed local recurrence at the site of their treated lesion at a median of 13 months after SRS. 20 patients (65%) developed recurrent disease in the CNS outside of the radiosurgery field at a median of 11 months after SRS. 4 patients developed toxicity from SRS related to radiation treatment effect, all of which occurred within 1 year of SRS. CONCLUSIONS: SRS for malignant CNS lesions in the pediatric population provides effective local control and is well-tolerated. However, there remains a substantial risk of distant CNS failures given the nature of recurrent or metastatic disease in these patients.