93 patients (22 proton CSI, 31 proton focal, and 40 surgery only) received annual neurocognitive evaluations for up to 6 years, including Full Scale IQ (FSIQ), Verbal Comprehension (VCI), Perceptual Reasoning (PRI), Working Memory (WMI), and Processing Speed Index (PSI) scores.

This study found that the proton focal and surgery only groups exhibited stable neurocognitive scores over time across all indexes (all p>0.05). In the proton CSI group, WMI, PSI, and FSIQ scores declined significantly (p=0.036, 0.004, and 0.017, respectively), while VCI and PRI scores were stable (all p>0.05).

This study concluded that outcomes were similar whether patients received focal PRT or no radiotherapy, but proton CSI emerged as a neurocognitive risk factor, consistent with photon outcomes research.