Systematic review and meta-analysis of photon radiotherapy versus proton beam therapy for pediatric intracranial ependymoma: TRP-ependymoma 2024

Introduction: Proton beam therapy (PBT) may reduce the number of adverse events in treatment of patients with pediatric cancer. However, it is difficult to evaluate whether the actual therapeutic effect is truly equivalent to that of photon radiotherapy. To compare photon radiotherapy and PBT, a meta-analysis and systematic review were performed. Methods: The meta-analysis used papers from 1990 to 2023 in which postoperative local photon radiotherapy or PBT was performed for pediatric intracranial ependymomas. Fifteen articles (5 PBT, 9 photon radiotherapy, one both) were selected based on administration of radiotherapy as local irradiation. Results: Among the 15 chosen articles, the 1- to 5-year overall survival (OS) rates (photon radiotherapy vs. PBT) were 95.4 % (95 % confidence interval (CI) 92.8–97.1 %) vs. 97.2 % (95.7–98.2 %); 88.3 % (85.0–90.9 %) vs. 93.5 % (91.4–95.1 %); 81.2 % (76.9–84.8 %) vs. 91.1 % (88.4–93.2 %); 76.9 % (71.2–81.6 %) vs. 86.1 % (81.9–89.4 %); and 73.8 % (68.3–78.5 %) vs. 84.7 % (79.9–88.5 %), respectively. The 1- to 5-year local control (LC) rates (photon radiotherapy vs. PBT) were 90.9 % (95 % CI 83.9–94.9 %) vs. 91.0 % (88.7–92.9 %); 81.5 % (68.9–89.4 %) vs. 85.7 % (82.0–88.6 %); 77.3 % (62.8–86.8 %) vs. 82.6 % (79.1–85.5 %); 74.6 % (57.7–85.6 %) vs. 78.3 % (71.6–83.5 %); and 72.6 % (51.4–85.8 %) vs. 79.0 % (73.4–83.5 %), respectively. The meta-regression analysis identified relationships of modality (photon radiotherapy vs. PBT), age at irradiation, pathology (Grade 2 vs. Grade 3), and tumor removal (complete resection vs. none) with significantly better 3-year OS after PBT and better 1- to 5-year LC at a younger age. Conclusion: In postoperative local irradiation of ependymomas in children, proton beam therapy had outcomes comparable to those of photon radiotherapy.