Glioblastoma treated by Stupp regimen (Temozolomide + radiation therapy) have a different outcome depending on the methylation status of MGMT gene: when the gene is unmethylated, the repair process is active and the prognostic poor. In pre-clinical models, it has been demonstrated that Folic acid could re-methylate the MGMT gene and therefore the repair process to radiation and temozolomide could be limited, allowing a better prognosis. The proposed phase-1 study will explore the safety and efficacy of escalated doses of oral Folinic acid concomitantly with Stupp regimen. To determine the MTD is the main objective of the study, then the toxicty profile, the RDP2 and the methylation process efficacy at the MGMT gene level.