Proton versus Photon Radiotherapy in Adults with Primary Brain Tumors Evaluating Functional Survival: A Phase 3 Randomized Controlled Trial Study Protocol (PRIDE)

Background: Radiation therapy (RT) plays a significant role in the multimodal management of primary brain tumors, improving oncological outcomes. However, despite advances such as Intensity-Modulated Radiation Therapy (IMRT), photon-based RT inevitably exposes normal organs to low-dose radiation, leading to long-term functional morbidities like cognitive decline, neuroendocrine dysfunction, auditory toxicity. These late effects are particularly concerning in patients with favorable prognoses and protracted survival. Proton beam therapy (PBT), owing to its unique physical properties, holds promise for better functional preservation, but robust clinical data in adults are lacking. Methods: The PRIDE study is a prospective, open-label, phase 3 randomized controlled trial enrolling adults aged 18–70 years undergoing focal cranial RT with conventional fractionation for primary brain tumors with expected survival >5 years at Tata Memorial Centre, Mumbai. Participants will be randomized 1:1 to receive either photon-IMRT (standard arm) or PBT (experimental arm), stratified by age, tumor type, proximity to the hypothalamic-pituitary axis, and radiation dose. The primary endpoint is 5-year functional survival, defined as survival without functional deterioration (neurocognitive decline, significant ototoxicity, new or worsening neuroendocrine dysfunction, neurological impairment, severe radio-necrosis, disease progression, or death). Secondary endpoints include patient-reported quality of life and health economic analysis. Statistical Analysis: Survival outcomes will be analyzed using Kaplan-Meier methods with log-rank test. Neurocognitive and quality-of-life data will be evaluated using linear mixed-effects and non-parametric tests. A total of 156 patients will be enrolled, accounting for 20% attrition, to detect a 25% absolute improvement in 5-year functional survival favoring PBT (65% vs 40%, HR 0.47, α=0.05, power=80%). An interim analysis has been planned using the O'Brien-Fleming rule after 50% of the events (n=28). Conclusion: This trial will provide level 1 evidence investigating the role of PBT in functional outcomes among adults with primary brain tumors, guiding future neuro-oncology practice. Ethics and Dissemination : The trial has been approved by the Institutional Ethics Committee of Tata Memorial Centre, Mumbai. Registration: The trial has been registered with the Clinical Trial Registry of India (CTRI/2025/03/082568) and Clinicaltrials.gov (study identifier NCT06831461).