Proton therapy for newly diagnosed pediatric diffuse intrinsic pontine glioma

Introduction: Diffuse intrinsic pontine glioma (DIPG) is a type of brain malignancy with a very poor prognosis. Although various radiation and chemotherapy protocols have been attempted, only conventional radiotherapy has yielded improvements in survival. In this study, we aimed to compare proton therapy versus conventional photon radiotherapy in terms of the outcomes of pediatric patients with DIPG.

Methods: This retrospective review included 12 pediatric patients with newly diagnosed DIPG who received a total proton therapy dose of 54 Gy (relative biological effectiveness) in 30 fractions at the University of Tsukuba Hospital between 2011 and 2017 (proton group). We additionally reviewed the medical records of 10 patients with DIPG who previously underwent conventional photon radiotherapy at our institute (historical cohort).

Results: The median progression-free survival (PFS) duration was 5 months (range 1-11 months), and the 6-, 12-, and 18-month PFS rates were 50%, 33%, and 25%, respectively. The median overall survival (OS) duration was 9 months (range 4-48 months), and the 6-, 12-, 18-, and 24-month OS rates were 66.8%, 50%, 41%, and 20%, respectively. There were no significant differences in survival between the proton and historical groups (PFS, p = 0.169 and OS, p = 0.16).

Conclusions: Proton therapy was well tolerated by the majority of patients. No severe adverse events, including radiation necrosis, were recorded. Proton therapy did not yield superior survival outcomes vs. conventional photon radiotherapy in patients with DIPG at our institution. Further research is needed to identify the factors associated with better survival in this population.