Before treatment, you will have a complete physical exam and blood (around 2 tablespoons) will be collected for routine tests. You will have either a magnetic resonance imaging (MRI) scan or a computed tomography (CT) scan of the brain. Women who are able to have children must have a negative blood pregnancy test. You will then meet with a study dietician. The dietician will give you written instructions and make a food plan based on your needs. The instructions and food plan will help you maintain a methionine-free (or reduced) diet during the study.