ARISTOCRAT: Blinded Trial of Temozolomide +/- Cannabinoids

Inclusion Criteria: * Histological diagnosis of MGMT promoter methylated, IDH wild type (WT) GBM with consistent local molecular pathology (repeat biopsy at recurrence is NOT required). * First recurrence of GBM planned for systemic treatment as determined by local Multidisciplinary Team (MDT), including agreement of a Consultant Neuro-Radiologist that imaging changes are most in keeping with recurrence and not pseudo-progression. Patients with a prior recurrence treated by surgical resection alone are eligible at time of first recurrence planned for systemic treatment. * Patients must have received initial first-line treatment with standard dose conventionally fractionated radiotherapy (i.e. 40 Gy in 15 fractions or 54-60 Gy in 28-33 fractions; other regimes may be considered in consultation with the ARISTOCRAT Trial Office) with concomitant and adjuvant TMZ. * A minimum of 3 cycles of adjuvant TMZ must have been received. * A minimum of Stable Disease (SD) (or Partial Response (PR)/Complete Response (CR)) at the end of first-line treatment (measured by Response Assessment for Neuro-Oncology (RANO) criteria). * ≥3 months since day 28 of the last cycle of TMZ. * Karnofsky Performance Status ≥60. * Adequate hematologic, renal, and hepatic function within 14 days prior to randomisation: * Absolute neutrophil count (ANC) ≥1.5 x 109/L * Platelet count ≥100 x 109/L * Serum creatinine clearance (measured or calculated (using local standard practice)) \>30ml/min * Tot…