Patients with grade 2 and 3 gliomas who received photon radiation therapy as part of their standard treatment are at risk of developing cognitive impairments, depending on the tumor's location and the size of the target volume. The extent to which these are caused in individual cases by the brain tissue within the target volume, which is necessarily exposed to a high dose, or whether they can be modified by differences in the exposure of surrounding brain regions exposed to low or moderate doses, is unknown. With the help of proton therapy, the risk of neurocognitive dysfunction could potentially be reduced by decreasing the brain volumes outside the target volume that are exposed to radiation therapy and receive a low dose. Based on current knowledge of relative biological effectiveness, the efficacy of proton therapy on the tumor compared to photon therapy can be considered equivalent with lower levels of uncertainty. In the present study, the impact of photon irradiation versus proton irradiation on neurocognition will now be directly compared. A bicentric, randomized study will investigate whether treating patients with WHO Grade 2 and 3 gliomas with proton radiation results in a different temporal course of neurocognitive function after treatment compared to photon radiation therapy.