The biomarker of interest may provide information regarding grade (indolent versus aggressive), stage (size and local spread beyond primary site), tumor biology (increased versus decreased cell proliferation, e.g., EGFRvIII is associated with increased proliferation of glioma cells), prognosis (increased versus decreased survival, e.g., IDH1 mutation is an independent factor for longer survival in GBM patients compared to patients with wild-type IDH1) and treatment response information, when analyzed before and after a chosen therapy (surgery, radiation therapy, systemic therapy) [183,184]. The gene discussed is IDH1; the disease is glioblastoma.