Treatment with chemotherapy as part of the initial treatment was the most powerful discriminator for a longer survival, with a median OS of 20.5 vs. 7.8 months (patients with vs. without adjuvant CHT; p < 0.001) and 18.7 vs. 7.9 months (patients with RCHT vs. patients with mono-RT; p = 0.002) (Fig. 2). Furthermore, ECOG (p = 0.008), MGMT (p = 0.03) and the extent of resection (p = 0.014) were significant predictors for a longer OS. Younger age (median 69.6 years, p = 0.216) and a shorter interval between surgery and the onset of RT (median 28 days, p = 0.82) were not associated with longer survival (Fig. 3). Postoperative ischemia was not significantly (p = 0.052) influencing overall survival, however, this might be a matter of numbers. All results from Cox regression analysis are summarized in Table 2.Fig. 2Survival stratified for Radiochemotherapy (a), adjuvant Chemotherapy (b), and e treatment (39 patients with imaging-defined recurrent GBM) (c) Fig. 3Overall survival of elderly patients stratified by Age (a), ECOG (b), Extent of Resection (c) and MGMT (d) Table 2Cox regression analysisCox regressionHR95% CI p Age (older vs. younger than 69.6 years)1.440.81–2.540.216ECOG ( 2–3 vs. 0–1)2.351.28–4.340.008MGMT (negative vs. positive)a 2.631.04–6.660.03Extent of resection ( GTR vs. STR & Biopsy )0.470.25–0.8760.014Ischemia (ischemia vs. no ischemia)b 1.940.98–3.820.059Time from surgery to RTx (earlier vs. later than 28 days)1.070.61–1.890.816Adjuvant CHT vs. No Adjuvant CHT0.240.13–0.47<0.001RCHT vs. RT0.380.21–0.690.002Treatment for recurrent disease (Treatment vs. BSC)c 0.060.02–0.17<0.001 aonly patients with measured MGMT methylation; bonly patients with postoperative imaging including DWI b1000 and ADC; conly patients with recurrence diagnosed by imaging