77 patients (38 proton and 39 photon) were evaluated with a median follow-up time of 2.2 years. This study reported no significant differences in symptomatic adverse events between the two groups: grade ≥ 2 adverse events were seen in 4 (10.5%) patients in the proton group and 3 (7.7%) in the photon group (p = 0.67). Proton therapy was associated with significantly higher rates of T1c+T2 changes on MRI (26.8%) at 2-year compared with 5.3% of photon therapy (p = 0.02), but severe adverse events were uncommon in both groups and survival outcomes were comparable between the two groups.