BACKGROUND: An increase of mutations as we age is well documented in GBM and in cancer in general. Elderly patients with GBM may have higher mutational burden and may be more likely to respond to immunotherapies. NUTMEG is a randomised Phase II study comparing post radiation NivolUmab and TMZ versus TMZ alone in Elderly patients with newly diagnosed GBM. METHODS: 102 patients will be randomized in a 2:1 allocation to receive short course RT (40Gy/15 daily fractions) and TMZ 75mg/m2) followed by 6 cycles of adjuvant TMZ (150-200mg/m2 days (D) 1-5 q28 days) with Nivolumab (240 mg D1, 15 q28 days for cycles (C) (1-4; 480 mg D1 Q 28 days for C5-6) versus 6 cycles of adjuvant TMZ (150-200mg/m2 D1-5 q28) alone. The study is stratified for ECOG performance status, age (< 70 vs = 70), MGMT methylation and extent of resection. An independent safety monitoring committee is overseeing the trial and will review safety data for the first 10 patients treated on the experimental arm (TMZ + Nivolumab). The primary endpoint is Overall Survival (OS). Secondary endpoints include: 6 month Progression Free Survival, adverse events (AEs) and immune AEs, Quality of life, neurological function (NANO Scale), and correlation of modified RANO and iRANO in the experimental arm. Translational research endpoints include correlation of clinical endpoints with mutational burden, comprehensive immune characteristics and novel MRI sequences including pHweighted MRIs. The expected proportion of patients alive at 24 months is predicted to be 15. 7%. A hazard ratio of more than 0. 69 in favour of the Nivolumab + TMZ arm will be considered sufficient to warrant further investigation including converting this study into a phase III trial. PROGRESS: At 10 August 2018, 8/18 study sites are open in Australia with 8 patients randomized. ACTRN12617000267358.