Currently, the optimal treatment regimen for elderly Glioblastoma (GBM) patients with poor performance status (PS) is unknown. Based on data for elderly GBM patients and the limited data for patients with poor PS, hypofractionated RT or a short course of Temozolomide (TMZ) may provide survival benefit without the added toxicity and inconvenience of a more protracted treatment regimen.

In particular, treatment with RT or TMZ monotherapy on the basis of methylated O6 - methyl guanine - DNA methyltransferase (MGMT) promoter methylation status, followed by the alternative therapy at progression, may provide a safe and effective treatment regimen for patients with poor PS.

The hypothesis of this trial is that in elderly GBM patients with poor performance status (age ≥ 65 years and KPS 60-70), a chemotherapy alone (TMZ monotherapy) approach to therapy results in non-inferior overall survival compared to combined TMZ/RT.

It is hypothesized that chemotherapy will result in non-inferior progression-free survival, reduced toxicity and increased cost-effectiveness compared to combined chemoradiotherapy.

Primary objective:

• To compare overall survival of standard therapy vs chemotherapy in elderly and frail patients with newly diagnosed GBM.

Secondary objective:

• To evaluate progression-free survival following treatment in both arms.
• To evaluate adverse events according to CTCAE criteria in both arms.
• To evaluate health-related quality-of-life as assessed by MoCA and EORTC QLQ-C30/QLQ-BN20 questionnaires in both arms.
• To evaluate cost-effectiveness of standard therapy vs chemotherapy

Methods:

Patients will be randomized to two treatment groups in a 1:1 ratio. Standard Arm: Combined modality arm Chemo-radiotherapy consisting of 40 Gy in 15 daily fractions with concurrent TMZ. TMZ will be delivered at a dose of 75 mg/m2 daily for 21 days. TMZ will be administered 1 hour before each session of RT.

After a 4-week break, patients will receive adjuvant TMZ according to the standard 5-day schedule (days 1-5) every 28 days, up to 6 cycles as tolerated by the patient. The dose will be 150 mg/m2 for the first cycle and increased to 200 mg/m2 beginning with the second cycle, so long as there are no hematologic adverse events, intractable nausea or fatigue. If tolerated, additional cycles of adjuvant TMZ may be administered at the treating investigator's discretion according to site practice.

Investigational Arm: TMZ monotherapy Patients will receive TMZ at a dose of 75 mg/m2 daily for 21 days, followed by adjuvant TMZ according to the standard 5-day schedule (days 1-5) every 28 days, up to 6 cycles as tolerated by the patient. The dose will be 150 mg/m2 for the first cycle and increased to 200 mg/m2 beginning with the second cycle, so long as there are no hematologic adverse events, intractable nausea or fatigue. If tolerated, additional cycles of adjuvant TMZ may be administered at the treating investigator's discretion according to site practice.

Upon treatment completion, participants will be followed by every 2 and 3 months for 2 years. Response and progression will be evaluated using the new international criteria proposed by the Response Assessment in Neuro-Oncology working group (RANO).

Inclusion Criteria:

1. Newly-diagnosed, histologically proven, intracranial glioblastoma with maximal safe resection. Biopsy alone is expected if resection is not possible. MGMT promoter methylation status must be tested and the results positive (defined as all non-negative MGMT status, including intermediate or indeterminate status (i.e., with cutoff higher than the MGMT negative threshold).

2. History and physical examination, including neurological examination, within 14 days prior to randomization.

3. Age ≥ 65 & KPS of 60 - 70

4. Stable or decreasing dose of corticosteroids for at least 14 days prior to randomization.

5. Laboratory evaluation within 7 days prior to randomization, with adequate function as defined below:

   1. ANC ≥ 1.5 x 109/L
   2. Platelets ≥ 100 x 109/L
   3. Serum creatinine ≤ 1.5 times ULN or estimated Glomerular Filtration Rate (eGFR) > 59
   4. Total serum bilirubin ≤ 30 umol/L (ie ≤ 1.5 times ULN)
   5. ALT < 150 U/L (ie < 3 times ULN)
   6. AST < 120 U/L (ie < 3 times ULN)
   7. Alkaline phosphatase < 390 U/L (ie < 3 times ULN)

6. Patients must sign a study-specific informed consent prior to study registration.

7. Patients of childbearing / reproductive potential should use highly effective birth control methods, as defined by the investigator, during the study treatment period and for a period of 6 months after the last dose of study drug. A highly effective method of birth control is defined as those that result in low failure rate (i.e. less than 1% per year) when used consistently and correctly.

   Note: abstinence is acceptable if this is established and preferred contraception for the patient and is accepted as a local standard.

   1. This will apply for male patients only and their female partner if of child bearing potential.
   2. Effective contraception should also be used by male patients taking temozolomide. Men being treated with temozolomide are advised not to father a child during or up to 6 months after discontinuation of treatment (male patients).

8. Male patients should agree to not donate sperm during the study treatment and for six months post treatment completion.

Exclusion Criteria:

1. Negative MGMT promoter methylation status, or a status of not reportable.

2. Recurrent malignant gliomas

3. Prior invasive malignancy (except for non-melanomatous skin cancer) unless disease free for ≥ 3 years.

4. Prior head or neck RT (except for T1 glottic cancer), or systemic therapy precluding delivery of concurrent and adjuvant temozolomide

5. Treatment with any other therapeutic clinical protocol within 30 days prior to study registration or during participation in the study.

6. Severe, active co-morbidity, defined as follows:

   1. Unstable angina and/or congestive heart failure requiring hospitalization
   2. Transmural myocardial infarction within the last 6 months
   3. Acute bacterial or fungal infection requiring intravenous antibiotics at the time of study registration
   4. Any severe, active co-morbidity precluding delivery of temozolomide.
   5. History of hypersensitivity reaction to temozolomide components or to dacarbazine.
   6. Active HBV infection