A Dose Finding Study of [177Lu]Lu-DOTA-TATE in Newly Diagnosed Glioblastoma in Combination With Standard of Care and in Recurrent Glioblastoma as a Single Agent.

Eligibility Criteria

• * Participant is \>= 18 years on the day of signing informed consent form
• * Histologically confirmed glioblastoma
• * Adequate bone marrow, organ function and electrolyte values
• * Presence of Gadolinium enhancing tumor in pre-surgery magnetic resonance imaging (MRI)
• * Karnofsky Performance Score (KPS) \>= 70 %
• * Evidence of recurrent disease demonstrated by disease progression using modified Response Assessment in Neuro-Oncology (mRANO) criteria
• * KPS \>= 60 %
• * \[68Ga\]Ga-DOTA-TATE uptake by positron emission tomography/computed tomography (PET/CT) or PET/MRI at the tumor region
• * Presence of Gadolinium enhancement in the tumor region in MRI at the time of diagnosis of tumor recurrence
• * A second surgery for glioblastoma is allowed provided that the following criteria are met:
• 1. Residual and measurable disease post-surgery is not required but surgery must have confirmed the diagnosis of recurrence
• 2. Surgery completed at least 2 weeks prior to study treatment initiation, with post-surgery recovery without any complications related to surgical procedure
• * Patients experiencing first recurrence of their glioblastoma, after standard or experimental therapy that includes prior EBRT
• * Participant is receiving additional, concurrent, active therapy for glioblastoma outside of the trial
• * Extensive leptomeningeal disease
• * History of another active malignancy in the previous 3 years prior to study entry
• * Prior administration of a radiopharmaceutical unless 10 or more effective half-lives have elapsed before injection of \[68Ga\]Ga-DOTA-TATE or \[177Lu\]Lu-DOTA-TATE
• * Early disease progression prior to 3 months from the completion of radiotherapy
• * Previous treatment with bevacizumab for the treatment of glioblastoma with therapeutic intent, or with bevacizumab as supportive therapy (e.g. edema reduction) within 60 days of initiation of study treatment