The global landscape of particle beam radiotherapy trials over the past 15 years

This study comprehensively analyzed 416 global particle beam radiotherapy (PBRT) trials (2007–2023), the first to systematically characterize the PBRT trial landscape with direct proton vs. carbon ion comparisons. Key findings: 70% of trials were phase I/II with small samples; carbon ion trials concentrated in Asia (77.1%), mostly government-funded, and strictly excluded the elderly (61.8%); proton trials dominated in North America, with larger samples and higher randomization rates. Trials declined post-2021; early termination mainly resulted from slow accrual (68.6%). Clinically, PBRT remains exploratory—needs global collaboration to standardize carbon ion RBE models, government funding for large phase III trials, relaxed age restrictions in carbon ion studies, and reference to photon radiotherapy’s standardized design to address current limitations and advance PBRT’s clinical translation.