A comprehensive review of randomized controlled trials (RCTs) reveals that temozolomide, when used in both concomitant and adjuvant phases, significantly improves overall survival (OS) and progression-free survival (PFS) in patients with glioblastoma multiforme (GBM), a form of high grade glioma (HGG), compared to radiotherapy alone. However, it is associated with an increased risk of early adverse events. In elderly patients, temozolomide alone shows comparable survival benefits to hypofractionated radiotherapy but with a higher incidence of adverse events. In recurrent HGG, temozolomide improves PFS but does not enhance OS.