In newly diagnosed glioblastoma patients aged 70 years or older who are suitable for concurrent temozolomide, the optimal dose of radiation therapy is controversial . The purpose of this study is to compare conventional radiotherapy of 60 Gy (6 weeks) versus hypofractionated radiotherapy of 40 Gy (3 weeks) in terms of overall survival as the primary endpoint along with progression-free survival, toxicity, quality of life, and prognostic biomarkers.

Inclusion Criteria:

• newly diagnosed glioblastoma according to the 2021 World Health Organization classification
• interval of ≤4 weeks between pathological diagnosis and randomization
• aged 70 years or older
• gadolinium-enhanced MRI within 72 hours of surgery
• known o6-methylguanine-DNA-methyltransferase promoter methylation status
• Karnofsky performance score ≥60
• stable or decreasing dose of steroid (if necessary)
• no history of brain radiotherapy
• no history of any systemic chemotherapy
• adequate hematological, renal and hepatic functions for temozolomide
• able to start radiotherapy within 3 weeks from randomization

Exclusion Criteria:

• patients with spinal leptomeningeal carcinomatosis
• history of cancer other than the followings:
• carcinoma in situ of the cervix
• completely excised non-melanoma skin cancer
• cancers without any evidence of residual disease for 5 years or longer
• patients with serious active infection or other serious underlying medical conditions
• patients with psychological issues that cannot comply to the protocol
• patients with known hypersensitivity to temozolomide or compounds with similar chemical composition to temozolomide
• patients who are currently participating in other clinical trials

There is no plan to make individual participant data available.