This trial is a translational, open-label, monocentric prospective study of 80 patients aiming to study resistance mechanisms as well as biomarkers of resistance or sensitivity to TTFields. The study will be conducted on a population of patients with newly diagnosed glioblastoma treated with radio-chemotherapy followed by TTFields in the context of either routine care or a clinical trial. In this study, the Optune® system (battery operated device which delivers TTFields to the brain) will not be under investigation. For each included patient, blood samples will be collected during baseline visit (before initiation of radio-chemotherapy), then before initiation of TTFields and every 3 months during TTFields treatment. Additional blood samples will be scheduled at recurrence (if applicable). Moreover, tumor samples (formalin paraffin embedded (FFPE) tumor block and fresh samples) will be collected from surgery specimen on primary tumor by the sponsor for analysis. In case of recurrence, and if a second surgery is possible, tumor samples will also be collected. Tumor samples will be collected from biopsies taken in the course of routine practice and from surgical specimens collected during surgical procedure. No additional biopsies will be performed for the study. Patients will be followed-up for time to progression and overall survival for a maximum duration of 24 months from the TTFields initiation. MRI performed by patients during the course of the study will be collected by the sponsor for additional future research purposes.