BACKGROUND: The EORTC (26981-22981)/NCIC CTG (CE.3) RCT in newly diagnosed GBM showed increased survival with concomitant and adjuvant temozolomide (TMZ) added to radiotherapy (RT). Study pts were 18-71 (median 56) years; however a sub-group analysis noted a trend of decreasing benefit from the addition of TMZ with increasing age, such that for age 65-71, the hazard ratio of 0.8 did not reach statistical significance (p = 0.340). This may reflect a lack of efficacy in elderly patients, or simply be due to a lack of statistical power in this subgroup. Recent RCTs in elderly GBM found improved survival with RT compared to supportive care alone and detected non-inferiority of 40 Gy/15 vs. a 60 Gy/30 RT regimen and superior survival was noted for MGMT-methylated patients treated with TMZ alone vs RT alone. Based upon these results short-course hypofractionated RT is often recommended for elderly pts. However, whether the addition of TMZ to RT confers a survival advantage in elderly pts, particularly for those with methylated MGMT, remains unanswered. METHODS: We conducted a global randomized phase III clinical trial for patients ≥65 yrs of age with histologically confirmed newly diagnosed glioblastoma, ECOG 0-2, randomized 1:1 to receive 40Gy/15 RT vs. 40Gy/15 RT with 3 weeks of concomitant temozolomide plus monthly adjuvant TMZ until progression or 12 cycles. Stratification is by centre, age (65-70, 71-75, or 76+), ECOG 0,1 vs 2, and biopsy vs resection. RESULTS: Accrual of n = 562 patients was completed Sept 19, 2013. Accrual by participating group was NCIC CTG 199, EORTC 249, TROG 97, and Japan 17 patients. Median age of randomized patients was 73 (65-90) years with 70% of patients over the age of 71. The study was powered to detect a HR of 0.75 in median OS, requiring 520 events for analysis. At the time of writing the required number of deaths had not been reached. A comprehensive analysis, including MGMT promoter methylation and QOL, is planned. CONCLUSIONS: A global cooperative group trial was completed randomizing 562 elderly patients with glioblastoma. The final results will add to our knowledge on the optimal treatment of these patients. SECONDARY CATEGORY: n/a.