2371 - Stereotactic Radiosurgery for Recurrent Primary and Metastatic CNS Malignancies in the Pediatric Population
Presenter(s)
M. Gribble1, D. Raleigh2, P. K. Sneed3, L. Boreta3, A. Reddy1, A. Banerjee4, S. Mueller1, K. I. Auguste1, N. Gupta1, and S. E. Braunstein3; 1University of California San Francisco, San Francisco, CA, 2Department of Radiation Oncology, University of California, San Francisco, San Francisco, CA, 3Department of Radiation Oncology, University of California San Francisco, San Francisco, CA, 4University of California, San Francisco, San Francisco, CA
Purpose/Objective(s): 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 group of patients.
Materials/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 (43 total treatments), and ten patients were treated for brain metastases (12 total treatments). Primary CNS histologies included ependymoma, glioma, meningioma, and medulloblastoma. At diagnosis, 26% were WHO grade 2, 52% were grade 3, and 22% were grade 4. Brain metastases included non-germinomatous germ cell tumors, chordoma, and osteosarcoma. 70% of patients had prior involved-field external beam radiation (RT) to the brain (median dose 59.4 Gy in 33 fractions, range [50.4-59.4 Gy] in 27-33 fractions). Median age at SRS was 12 years (range 4-21). SRS was largely performed in a single fraction (median dose 18 Gy, range 11-20. The median SRS gross target volume (GTV) was 1.3 cc (range 0.06 – 21.1) and the median fractionated-SRS GTV was 23.2 cc (range 8.5 – 44.8). Median follow up after SRS was 33 months (IQR 14-56). 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 80.0%. 9 patients (24%) had no evidence of intracranial disease after SRS at a median follow up of 37 months. 19 patients (51%) developed distant brain recurrence without local failure at a median of 8 months after SRS. LC, IC-PFS, and OS did not significantly differ based on tumor histology or WHO grade, though patients who received SRS to a single lesion had significantly higher IPFS compared to those with 2-4 or =5 lesions (3-year IPFS 32.2%, 6.7%, and 0% respectively, p=0.005). All patients with subsequent CNS recurrence after SRS underwent salvage therapy, including additional radiotherapy, systemic therapy, and/or resection. In total, 2 patients developed CTCAE grade 3 toxicity from SRS, both of which were related to radiation treatment effect and occurred within 1 year of SRS. On univariate analysis, there was no significant association of development of adverse radiation effects (ARE) with GTV, V10Gy, V12Gy or prior RT.
Conclusion: SRS for malignant CNS lesions in the pediatric population provides effective local control with low toxicity risk. Although there remains a substantial risk of distant CNS failures after SRS, all patients were able to receive additional salvage therapy including re-irradiation. This study supports the use of SRS as a treatment modality for focally recurrent pediatric CNS malignancies.