Imaging of glioblastoma recurrence

Glioblastoma is the most common primary malignant neoplasm of the brain in patients over the age of 50years. At initial diagnosis, the most typical MR imaging findings of glioblastoma include an intraaxial mass with irregular peripheral enhancement, peripheral diffusion restriction, central necrosis, and outer nonenhancing zone of T2 FLAIR hyperintensity. Following maximal safe surgical resection, MR imaging is routinely performed within 24-48hours to assess the adequacy of resection. Radiotherapy plus concomitant temozolomide is usually started 4-5 weeks following surgery. MR imaging surveillance begins approximately 1month following completion of concurrent chemo-radiation and continues every 3months thereafter. Early detection of tumor recurrence is the most important trigger for consideration of a change in therapeutic strategy. MRI is the primary imaging modality for initial diagnosis, immediate postoperative imaging, and posttreatment surveillance of glioblastoma. Molecular imaging techniques have also shown promise in differentiating recurrent tumor from treatment-related effects. The appearance of recurrent glioblastoma and posttreatment effects overlap significantly on conventional MR imaging. Advanced MR imaging and molecular imaging techniques have shown much better results in the differentiation of recurrent tumor from posttreatment effects. To date, much of the investigation in this area has focused on single imaging modalities. More recent investigations have shown improved diagnostic performance with the combination of multiple imaging modalities.