New advances that enable identification of glioblastoma recurrence.

Postoperative adjuvant radiation therapy and temozolomide chemotherapy have become the standard care for newly diagnosed malignant gliomas. The efficacy of these therapies has led to an increase in pseudoprogression and radiation necrosis, both of which are treatment-related effects whose appearance on standard MRI with gadolinium-based contrast agents resembles that of tumor progression or recurrence. Accurate diagnosis of these post-treatment lesions as either tumor recurrence or treatment effects (pseudoprogression or radiation necrosis) is important to determine the patient's prognosis. Modern advancements with magnetic resonance spectroscopy (MRS), diffusion-weighted imaging (DWI), and PET scans have shown promise for distinguishing tumor recurrence from treatment effects. Advances in radiographic techniques will become critically important with the emergence of new antiangiogenic therapies. Consequently, MRS, DWI, and PET need to be incorporated into routine post-treatment investigations to improve the specificity and sensitivity of distinguishing tumor recurrence from treatment effects. Further research will also be needed to develop improved algorithms that use these modalities, and to develop new modalities with even greater accuracy than those currently available.