TTFields Plus FET-PET-Guided Stereotactic Radiosurgery Versus TTFields Alone for Recurrent Glioblastoma (Tarrget 2.0)

Tumor Treating Fields (TTFields) Concomitant With Stereotactic Radiosurgery Based on FET-PET vs TTFields Alone for the Treatment of Recurrent, Glioblastoma (Tarrget 2.0)

This study evaluates whether the addition of FET-PET-guided stereotactic radiosurgery (SRS) to Tumor Treating Fields (TTFields) improves survival outcomes in patients with recurrent IDH-wildtype glioblastoma.

Patients with recurrent glioblastoma have limited treatment options and poor prognosis. TTFields is a non-invasive antimitotic therapy that has demonstrated efficacy in recurrent glioblastoma. Stereotactic radiosurgery is commonly used in selected patients with recurrent disease; however, treatment efficacy may be limited by the infiltrative nature of glioblastoma and challenges in accurate target delineation.

The study hypothesizes that combining TTFields with FET-PET-guided stereotactic radiosurgery will improve one-year overall survival compared with TTFields alone. Participants will be randomized in a 1:1 ratio to receive either TTFields plus stereotactic radiosurgery or TTFields alone.

Glioblastoma is the most common malignant primary brain tumor in adults and remains associated with poor prognosis despite multimodal treatment. There is currently no established standard therapy for recurrent glioblastoma, and outcomes remain unsatisfactory.

Tumor Treating Fields (TTFields) are low-intensity, intermediate-frequency alternating electric fields that disrupt mitosis and inhibit tumor growth. TTFields have demonstrated efficacy in recurrent and newly diagnosed glioblastoma with minimal systemic toxicity.

Stereotactic radiosurgery (SRS) is an established local treatment option for selected patients with recurrent glioblastoma. However, MRI-based target delineation may underestimate the true extent of infiltrative tumor growth. FET-PET imaging provides improved visualization of metabolically active tumor tissue and may improve treatment precision.

Preclinical studies suggest synergistic effects between TTFields and radiation therapy through increased radiosensitivity and modulation of DNA repair mechanisms. Additional immunomodulatory effects may further enhance treatment efficacy.

This prospective randomized single-center study will compare TTFields combined with FET-PET-guided stereotactic radiosurgery versus TTFields alone in patients with recurrent IDH-wildtype glioblastoma. The primary objective is to determine whether combined treatment improves the one-year overall survival rate.

Inclusion Criteria:

• Age ≥18 years
• Karnofsky Performance Status ≥70
• Histologically confirmed IDH-wildtype glioblastoma
• First, second, or third recurrence
• Radiological recurrence according to RANO 2.0 criteria
• Prior radiotherapy and temozolomide treatment
• At least 6 months since completion of previous radiotherapy
• Contrast-enhancing recurrent lesion visible on MRI
• Maximum recurrent lesion diameter ≤5 cm
• Available molecular profile including IDH and MGMT status
• Adequate hematologic, renal, and hepatic function
• Written informed consent

Exclusion Criteria:

• Previous bevacizumab treatment
• Planned chemotherapy or targeted therapy after study intervention
• Previous stereotactic re-irradiation within the planned treatment field
• More than three recurrences
• Significant psychiatric disorders
• Significant unrelated neurological disease
• Implanted pacemaker, defibrillator, deep brain stimulator, or other incompatible electronic device
• Pregnancy or breastfeeding
• Active intracranial hemorrhage
• Uncontrolled hypertension
• Severe renal dysfunction
• Participation in another interventional study likely to interfere with this study