KEY POINTS
- This single-centre retrospective study included 89 adults with recurrent glioblastoma treated with proton reirradiation between 2015 and 2025, plus a contemporaneous comparator cohort of 49 patients treated with photon reirradiation.
- All patients received 35 Gy in 10 fractions. In the proton cohort, median age was 58 years, median interval from initial radiotherapy to reirradiation was 15.5 months, 48% underwent reresection, and 81% received concurrent systemic treatment.
- Composite dosimetry showed that the initial radiotherapy course accounted for most cumulative exposure to the brainstem, optic chiasm, and optic nerves, while proton reirradiation contributed comparatively limited additional dose.
- Median overall survival was 8.3 months after proton reirradiation versus 7.2 months after photon reirradiation, with no significant difference between modalities. Six- and 12-month overall survival after proton treatment were 62.6% and 24.9%, respectively.
- Grade 3–4 radiation necrosis occurred in 5 of 89 proton-treated patients (5.6%) and 3 of 49 photon-treated patients (6.1%). No optic neuropathy, brainstem necrosis, or grade 5 toxicity was reported; increasing age remained independently associated with worse survival (hazard ratio 1.02 per year, 95% confidence interval 1.00–1.05; p=0.045).
CLINICAL TAKEAWAY
Hypofractionated proton reirradiation is a feasible salvage option for selected patients with recurrent glioblastoma, particularly when cumulative dose to the optic apparatus or brainstem limits photon planning. However, the study does not demonstrate improved survival or reduced toxicity versus photons, and its retrospective design, treatment-selection bias, short follow-up, and absence of systematic quality-of-life assessment limit conclusions.
SOURCE
International Journal of Radiation Oncology, Biology, Physics