The height of each MRS metabolite peak will be measured from voxels within the enhancing MRI lesion and from voxels in normal brain for each patient. Relative metabolite values (normalized to the value in normal brain) will then be generated, as well as relative metabolite ratios (eg. relative choline/relative NAA) for each time point (week 0, week 4, and post-RT, at follow-up). For each patient, the relative metabolite levels (and ratios) will be plotted over time. Patients will then be partitioned into groups, based on similar evolving MRS pattern. For each of the groups, curves of survival and disease free progression will be generated by the Kaplan-Meier method. The curves will be analyzed for statistical significance by the log-rank method.