The main objective is to identify using this triple approach (detection of the mutation on plasma DNA detection, detection of urinary D-2HG, detection of tumor D-2HG by spectro-MRI) patients with IDH1arg132His mutation, the secondary objective is to evaluate the value of these markers for patients follow-up and for differentiating recurrence from treatment induced damage. 40 patients with grade II and grade III gliomas (20 mutated, 20 non mutated) will be included and followed up for one year (five measurements are planned).