PET for therapy response assessment in glioblastoma

Glioblastoma (GB) is the most malignant and the most common type of glioma in adults, accounting for 60–70% of all malignant gliomas. Despite the current therapy, the clinical course of GB is usually rapid, with a mean survival time of approximately 1 year. For therapy response assessment in GB, magnetic resonance imaging (MRI) is the method of choice. In 2010, the Response Assessment in Neuro-Oncology (RANO) was introduced, including the tumor size (in 2D) as measured on T2-weighted and Fluid Attenuated Inversion Recovery (FLAIR)-weighted images, in addition to the contrast-enhancing tumor part. Although the RANO criteria addressed some of the limitations of the previous MacDonald criteria for therapy evaluation in high-grade glioma, treatment-related side effects hamper correct response assessment. To address the above-mentioned drawbacks in the follow-up of GB, incorporating changes in tumor biology measured by advanced MRI and positron emission tomography (PET) imaging, which may precede anatomical changes of the tumor volume, is promising. Imaging biomarkers capable of predicting response at an early time point after treatment initiation are the premise of personalized treatment enabling change or discontinuation of therapy to prevent ineffective treatment or adverse events of treatment. In this chapter, an overview of applicable PET tracers for the therapy response assessment in GB and the determination of tumor recurrence versus treatment-related effects is given.