No predictive factors are known for the response to the bevacizumab anti-angiogenic molecule (Avastin) given in the event of relapse of glioblastoma (GBM) following radiochemotherapy. Classical MRI with gadolinium injection and perfusion is not sufficient to predict survival and response or duration. We propose to evaluate the prognostic interest for 6-month survival of spectroscopic biomarkers of proliferation, glial reaction, infiltration and glutaminergic metabolism or glycolytic metabolism recorded at 7 and 28 days of application of the treatment. These biomarkers are based on the increase of an index combining choline / Creatine (Cho / Cr), Glx / Cr (Glutamine and glutamate / Creatine), NAA / Cr (N acetyl aspartate / Creatine) and lactate / Cr ratios. The long-term objective is to predict the survival of these relapsed GBM patients at an early stage and to identify responder patients who would benefit from this expensive molecule and avoid using it in non-responding patients