10176-RT-3 A Multi-Institutional Prospective Registry-Based Observational Study of Proton Therapy for Adult Gliomas

Abstract Objective A prospective multi-institutional registry study (Proton Net) has been conducted since May 2016, enrolling all patients undergoing proton therapy. Registered cases receive treatment in accordance with the guidelines established by the Japanese Society for Radiation Oncology, allowing evaluation of the safety and efficacy of proton therapy. This study reports treatment outcomes of glioma cases treated with proton therapy under advanced medical care up to June 2023. Methods We analyzed overall survival (OS), progression-free survival (PFS), and late adverse events in glioblastoma (GBM, n = 28), high-grade glioma (HGG, n = 17), and low-grade glioma (LGG, n = 9) cases registered in Proton Net. A systematic review comparing reported outcomes of proton vs. photon therapy was also conducted. Results The median observation period (months) for GBM, HGG, and LGG was 59.3, 54.6, and 41.2, respectively. In GBM, median OS/PFS was 21. 3/10. 9 months; the 1-/3-year OS rates were 81.5%/21.7%, and PFS rates were 41.1%/11.4%. In HGG, median OS/PFS was 54. 2/30.1 months; 1-/3-year OS rates were 88. 2%/53. 5%, and PFS rates were 76. 0%/29. 0%. All LGG patients remained alive and progression-free during the observation period. Late adverse events were observed in one GBM and one HGG case; the 3-year incidence of late toxicity was 4.4%, 6.6%, and 0% for GBM, HGG, and LGG, respectively. The systematic review of 14 articles suggested comparable efficacy and safety between proton and photon therapies across glioma types, although the observation period may be insufficient for LGG evaluation. Conclusion Short-term outcomes of proton therapy for gliomas appear comparable to those of photon therapy. Continued long-term follow-up and evaluations incorporating predictive models for adverse event risk are warranted.