External validation of a prognostic model estimating the survival of patients with recurrent high-grade gliomas after reirradiation

PURPOSE: We aimed to validate a controversial prognostic model for the survival of relapsed malignant glioma patients after reirradiation with an independent, multicentric patient cohort.METHODS AND MATERIALS: A total of 165 malignant glioma patients underwent reirradiation at 4 different institutions between 1994 and 2012. Twenty-two patients had a good (score 1), 44 had a moderate (score 2), and 99 had a poor prognosis (score 3 or 4). Four statistical methods were used to validate the prognostic model: First, we compared survival according to prognostic group in the construction and the validation cohort by visual comparison of the respective Kaplan-Meier plots. Second, discrimination was…