Radiosurgery for Recurrent Pediatric Brain Tumors: A Single Institution Experience

Abstract

This study evaluates the efficacy and safety of reirradiation using stereotactic radiosurgery (SRS) in recurrent pediatric primary brain tumors. This IRB-approved retrospective review included pediatric patients aged 2-23 years old with recurrent primary brain tumors treated at Stanford University from 2000 through 2019. Patients were treated with SRS using a frameless image-guided radiosurgery system. Prescription dose and fractionation were chosen based on tumor size and location as well as history of prior radiation. Local failure (LF) after SRS was defined as radiographic evidence of tumor progression within or adjacent to the SRS target volume. Distant intracranial failure (DIF) was defined as occurrence of new lesions in the brain outside of the SRS target volume. Time to LF and DIF was measured from date of SRS and was analyzed using competing risk analysis with death as a competing risk. Overall survival (OS) was calculated from the date of first SRS to the date of death or censoring and analyzed with the Kaplan-Meier method. In total, 29 patients aged 2-23 years old with a total of 34 lesions were included. The median age at diagnosis was 9.74 years. Eleven lesions were ependymoma, four were gliomas, eight were medulloblastomas, three were PNETs, one was a CNS embryonal tumor, and two were germ cell tumors. The mean target volume for the recurrences in this series was 3.85 ml (range, 0.05–42.5 ml). An average 76% isodose line (range, 64–91%) was used to deliver a mean prescription dose of 19.2 Gy (range, 12–27.5 Gy) to the periphery of the tumor. This prescribed dose was administered in an average of two sessions (range, 1–5). Mean clinical follow-up time was 45 months. The median OS after treatment for all patients was 25 months. Of the 34 lesions, 6 lesions had no follow-up scans and were not included in the analysis for distant or local failures. Of the 28 lesions with follow-up imaging, the 2-year cumulative incidence of LF after reirradiation with SRS was 12.3% [95% confidence interval (CI), 3.8% – 26.1%]. The 2-year cumulative incidence of DIF was 33.3% [95% confidence interval (CI), 17.9% – 49.6%]. A total of 2 patients subsequently presented with LMD after SRS. Twelve patients were treated with irradiation using repeat radiosurgery or conventional external beam following a subsequent progression. Three patients had radiation necrosis (10.3 %). Of these, two were symptomatic, including one patient who had new onset weakness improved with steroids while another patient developed ataxia and facial weakness with imaging showing mixed progressive tumor and necrosis. Reirradiation using SRS for recurrent pediatric brain tumors is safe and can achieve good local control. Innovations to improve both local and distant control should continue as prognosis remains poor.