We aimed to compare two different salvage treatment strategies for relapsed high-grade glioma (HGG) patients by means of a new prognostic model. A simplified version of the so-called HGG-Immuno RPA model estimates the prognosis of relapsed HGG patients and distinguishes three different prognostic classes (I = good, II = intermediate, III = poor). The model has been constructed with a cohort of 117 patients whose salvage treatment consisted of re-operation followed by dendritic cell vaccination (ReOP + DCV). However, using only the predictors histology, age and performance status, the simplified HGG-Immuno RPA model is basically independent from treatment. In the present study we applied the simplified model to the cohort used to construct the original HGG-Immuno RPA model and another cohort of 165 patients who underwent re-irradiation (ReRT) at relapse. Then, we compared the outcomes achieved by the two different salvage treatments in each prognostic class. The model predicted good, intermediate and poor prognosis for 11, 31 and 75 patients of the ReOP + DCV cohort and for 20, 39 and 106 patients of the ReRT cohort, respectively. Neither of the two strategies was superior to the other. In the groups with good, intermediate and poor prognosis 12-months survival rates were 73, 59 and 25 % after ReOP + DCV and 72, 36 and 23 % after ReRT, respectively. Being easy to handle and independent from treatment, the aforementioned model is useful for therapeutic decisions. ReRT and ReOP + DVC seem to be equally effective. The choice of salvage treatment should be based on the expected side effects.