Glioblastoma is an aggressive type of brain cancer. Standard treatment usually includes three weeks of radiation therapy alone or combined with chemotherapy using Temozolomide. After a four- to six-week break, more Temozolomide chemotherapy is usually given. However, some tumors have a marker ("unmethylated MGMT") that predicts the usual chemotherapy won't work. Because of this, this project will explore other treatment options to help slow the disease and improve survival. In this study, the same chemotherapy (Temozolomide) normally given after radiation therapy for glioblastoma. The only difference is that it will be given with a modified regimen.

Inclusion Criteria:

• Age ≥65 years.

• Histopathologically confirmed newly diagnosed WHO grade 4, IDH wild-type GBM

• Unmethylated MGMT promoter, according to local assessment

• Completed treatment with 40 Gy in 15 fractions over three weeks, with concurrent TMZ, within six weeks prior to enrollment

• Eastern Cooperative Oncology Group (ECOG) performance status scale of 0, 1, or 2.

• Karnofsky Performance Status (KPS) ≥60.

• Adequate organ function, as defined by the following laboratory values obtained within 28 days prior to enrollment:

  • Absolute neutrophil count (ANC) >1.5 × 10⁹/L (1,500 cells/mm³).
  • Platelet count >100 × 10⁹/L (100,000 cells/mm³).
  • Serum creatinine <1.5 times the upper limit of normal.
  • Total serum bilirubin <1.5 times the upper limit of normal.
  • ALT (SGPT) <2.5 times the upper limit of normal and/or AST (SGOT) <2.5 times the upper limit of normal.

• Signed informed consent (and assent, if applicable) must be obtained from the participant or their legal representative, ensuring the participant's ability to adhere to the study requirements.

Exclusion Criteria:

• Diffuse leptomeningeal involvement at the time of diagnosis.

• Inability to undergo contrast-enhanced magnetic resonance imaging (MRI)

• Known hypersensitivity to TMZ components or Dacarbazine

• Severe myelosuppression

• Active hepatitis B infection

• Severe or uncontrolled medical conditions (e.g., active systemic infection, diabetes, hypertension, coronary artery disease, or psychiatric disorders) that, in the investigator's judgment, could compromise patient safety or impede study completion.

• History of prior or second invasive malignancy, except for:

  • Non-melanoma skin cancer.
  • Completely resected cervical carcinoma in situ.
  • Low risk prostate cancer or under active surveillance.
  • Other cancers for which the subject has completed potentially curative treatment more than 3 years prior to study entry are allowed.