Radt-05. Mature Outcomes of a Phase Ii Prospective Study of Proton Radiotherapy for Localized Brain Tumors

Abstract BACKGROUND Proton radiotherapy (PRT) is a highly targeted form of radiation that spares more normal brain tissue compared to modern photon radiotherapy. Therefore, we expect the late effect profile in children treated with PRT with curable brain tumors should be improved. METHODS Between 2010-2022, 100 patients were enrolled, treated with PRT, and then followed for disease control, hearing, neurocognitive and endocrine outcomes. Late effects of the tumor and treatment delivered were graded using CTCAE v4.0. RESULTS Median age at PRT was 8.0 years (1.1-20.8) and median follow up was 8.7 years (0.3-12.7). Tumor types included 40 (40%) ependymomas, 19 (19%) low grade gliomas (LGG), 21 (21%) craniopharyngiomas, and 20 (20%) other histologies. 26% of patients were treated with chemotherapy in addition to PRT. The location of PRT was 38 (38%) infratentorial, 56 (56%) supratentorial, and 6 (6%) both. The median radiation dose was 52.2 GyRBE (48.6-59.4). 8-year event-free survival (EFS) and overall survival (OS) was 71.7% and 86.2% for all patients. 8-year EFS and OS was 59.9% and 82.4% for ependymomas, 78.2% and 94.7% for LGG, 80.0% and 87.7% for craniopharyngiomas and 79.1% and 84.7% for all other tumor types. 19% of patients had new grade 3+ toxicities that were at least possibly related to radiotherapy. Baseline full-scale intelligence quotient (FSIQ) was 98.0 and follow-up FSIQ was 101.8 (p=0.14). 43% of patients had new endocrine deficiencies after radiation. 8 patients suffered new high-grade hearing loss after PRT. Dosimetry on critical brain structures was collected and correlated with late effects. More details will be presented at the conference. CONCLUSION PRT remains an effective treatment for children with curable brain tumors. While late effects of the tumor and treatment are still present, the overall burden of late effects is lower than other reports.