Background/Aim: Previously, we identified predictors of survival after irradiation of grade II-IV cerebral gliomas. In this supplementary analysis, survival was calculated in a more appropriate way than the original study. Patients and Methods: Ten factors were re-evaluated for survival in patients of the original study including pre-radiotherapy seizures. In the original study, survival was calculated from the end of the last radiotherapy course (primary or re-irradiation). After re-review, this approach was considered inappropriate. Survival should have always been calculated from the first radiotherapy course, as done in this supplementary analysis. Results: On multivariate analysis, WHO-grade II (p=0.006) and upfront resection (p=0.001) were associated with better survival. Unifocal glioma was significant on univariate analysis (p=0.001), where a trend could be identified for age ≤59 years (p=0.057) and seizures (p=0.060). Conclusion: The findings of this supplementary analysis regarding the identification of prognostic factors for survival agree with the results of the original study.