RADT-11. PROTON BEAM THERAPY (PBT) FOR CENTRAL NERVOUS SYSTEM (CNS) TUMOURS IN CHILDREN: A CANADIAN PEDIATRIC BRAIN TUMOUR CONSORTIUM STUDY

Abstract

Abstract BACKGROUND Radiotherapy is important for treating pediatric CNS tumours. The main modalities include photon therapy and PBT. PBT offers potential advantages over photon therapy in children since its precise dose control can limit long-term side effects. However, Canadian patients needing PBT are referred to the United States (US) because PBT is unavailable in Canada. We aimed to describe PBT use and outcomes over time for Canadian pediatric patients with CNS tumours. METHODS Patient demographics, treatment characteristics, and outcomes were extracted from medical records of patients from 10/13 Canadian provinces/territories. Patients diagnosed with a CNS tumour at ≤20 years old between 2001-2021 who received curative-intent PBT were included. PBT plans were compared using Fisher’s exact or Kruskal-Wallis rank sum tests. Overall survival (OS) was estimated using the Kaplan-Meier method. RESULTS Of 195 patients (59.0% male) included in the study, majority were from Alberta (28.7%), Quebec (26.7%), British Columbia (22.6%), and Ontario (20.5%). Median age at diagnosis was 8.0 years. Most tumours (77.9%) were non-metastatic. Medulloblastoma was the most common diagnosis (30.8%). Provinces/territories referred patients to proton centres in the same geographical regions, except Alberta (74.5% referred to Florida). Referral numbers have increased ~180%/year since 2011. Median time from diagnosis to PBT was 126 days [11-5236] for all patients, and 36 days [21-1313] for medulloblastoma. Radiation doses, irradiation site, therapy duration, and time to treatment were not different (p≥0.2) across all PBT facilities for medulloblastoma. 5-year OS were 86.8% and 73.0% for the PBT study population and the Cancer in Young People-Canada reference population, respectively, in those aged <15 years. CONCLUSIONS Given the unavailability of PBT in Canada, pediatric CNS tumour patients were referred to US PBT facilities close in proximity. Further studies are needed to better understand provincial referral patterns and barriers to equitable PBT access across Canada.