Proton Bragg peak flash stereotactic radiosurgery for recurrent glioblastoma reirradiation

IF 3.2 Q2 ONCOLOGY

Physics and Imaging in Radiation Oncology Pub Date : 2026-07-01 Epub Date: 2026-07-20 DOI:10.1016/j.phro.2026.101044

Yangguang Ma, Yuyu Wang, Tengda Zhang, Xingyi Zhao, Balaji Selvaraj, Chingyun Cheng, Michael Pennock, Jocelyn Jackson, Wei Guo, Xuanqin Mou, Benjamin Durkee, Jehee Isabelle Choi, Haibo Lin, Charles B. Simone II, Minglei Kang, Hui Wu

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Abstract

Background and Purpose

Stereotactic Radiosurgery with robotic image-guided systems is promising for recurrent glioblastoma (rGBM), but long delivery times may increase morbidity and reduce accuracy. Proton single-energy Bragg-peak FLASH-RT (SEBP-FLASH) may address these limits by delivering each field in <1 s, with potential for normal-tissue sparing through the FLASH effect.

Materials and Methods

The SEBP-FLASH technique was used to reoptimize treatment for rGBM patients treated with robotic image-guided systems. Patient-specific aperture devices were incorporated into the SEBP-FLASH technique for sharper penumbra. The gross tumor volume (GTV) coverage, conformity index (CI), dose gradient index (GI₅₀ and GI₃₀), and dose-volume histogram (DVHs), were evaluated. Additionally, ultra-high dose-rate ratios in critical organs-at-risk were assessed.

Results

SEBP-FLASH successfully met all clinical objectives. Both SEBP-FLASH and robotic techniques showed comparable performance, with GI₅₀ and GI₃₀ values of 2.9 ± 0.5 and 6.2 ± 1.8 for SEBP-FLASH, versus 2.7 ± 0.2 and 5.5 ± 0.5 for robotic (p-values at 0.085 and 0.189). SEBP-FLASH demonstrated superior conformality, achieving a CI of 1.4 ± 0.2 compared to CK's 1.9 ± 0.3 (p-value 0.001). All other metrics were similar across both techniques. For the brain, the FLASH dose rate coverage (V_{40 Gy/s}) exceeded 80% under a 5 Gy dose threshold and minimum monitor unit of 400.

Conclusions

This study evaluated the dose-volume characteristics of SEBP-FLASH and robotic image-guided systems and found broadly comparable dose distributions, suggesting that SEBP-FLASH may be a feasible option for rGBM reirradiation. SEBP-FLASH also showed potential advantages in conformity, normal tissue sparing, and reduced on-table time.

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