Background: The EORTC (26981-22981)/NCIC CTG (CE.3) RCT in newly diagnosed glioblastoma (GB) showed increased overall survival (OS) with concomitant and adjuvant temozolomide (TMZ) added to radiotherapy (RT). Pts were 18-71 (median 56) years; however, a trend of decreasing benefit from the addition of TMZ with increasing age was noted. Recent RCTs in elderly GB detected non-inferiority of 40 Gy/15 v 60 Gy/30 RT and superior survival was noted for MGMT-methylated pts treated with TMZ alone. However, whether the addition of TMZ to RT improves survival in elderly pts remained unanswered. Methods: We conducted a global randomized phase III clinical trial for patients ≥ 65 yrs with histologically confirmed newly diagnosed GB, ECOG 0-2, randomized 1:1 to receive 40Gy/15 RT v 40Gy/15 RT with 3 weeks of concomitant TMZ plus monthly adjuvant TMZ until progression or 12 cycles. Stratification was by centre, age (65-70, 71-75, or 76+), ECOG 0,1 vs 2, and biopsy vs resection. Results: 562 pts were randomized, 281 on each arm; median age 73 yrs (range 65-90), male 61%, PS 0/1 77%, resection 68%. RT+TMZ significantly improved OS over RT alone (median 9.3m v 7.6m, HR 0.67, 95%CI 0.56-0.80, p < 0.0001) and significantly improved PFS (median 5.3m v 3.9m, HR 0.50, 95%CI 0.41 – 0.60, p < 0.0001). Tissue from 462 pts was provided and adequate for MGMT analysis in 354 to date. In MGMT methylated patients (n = 165) OS for RT+TMZ v RT was 13.5 m and 7.7m respectively (HR: 0.53 (95% C.I. 0.38, 0.73, p = 0.0001). In MGMT unmethylated patients (n = 189) OS for RT + TMZ v RT was 10.0m vs 7.9m respectively (HR 0.75 (95% C.I. 0.56 – 1.01, p = 0.055). QoL analyses showed no differences in functional domains of QLQC30 and BN20 but were worse in the RT/TMZ arm for nausea, vomiting, and constipation. Systemic therapy after PD was reported in 39% on RT+TMZ v 41% on RT. Conclusions: The addition of concomitant and adjuvant TMZ to hypofractionated RT for elderly pts with GB significantly improves OS and PFS in all patients and is well tolerated. Patients with MGMT methylated tumors benefit the most from the addition of TMZ to RT where median OS is nearly doubled. Clinical trial information: NCT00482677