PET Imaging in Glioma The Neuro-Oncologist’s Expectations Andreas F. Hottinger, MD, PhD a , Marc Levivier, MD, PhD a , Laura Negretti, MD b , Krisztian Homicsko, MD, PhD c , Roger Stupp, MD a, * INTRODUCTION Management of primary brain tumors and in particular glioma is a complex multidisciplinary exercise. The infiltrative nature of glioma does not allow one to easily demarcate tumor from normal tissue. Tumor location, that is, proximity to eloquent areas, does not permit resection with large safety margins, and radiation therapy is limited by the tolerance of normal brain tissue. Brain is protected by the blood–brain barrier (BBB), and many chemotherapeutic or targeted agents do not reach the tumor cells in adequate concentrations. In high-grade tumors, imaging is facilitated by contrast enhancement, reflecting disruption of the BBB, whereas low-grade glioma usually does not show contrast uptake. However, the absence of enhancement does not exclude a higher-grade tumor. Virtually all patients will present with tumor progression or recurrence, even after complete resection, followed by radiotherapy and chemo- therapy. 1 In low-grade glioma, watchful waiting and repeated clinical and radiological monitoring is commonly the favored approach in younger patients. 2 Adequate and early identification of tumor growth acceleration, malignant transforma- tion, tumor progression, or recurrence is important to determine antitumor therapy. The evaluation of treatment effect is challenging. Tumor response may be slow and delayed. Residual and recurrent tumor cannot easily be distinguished from treatment response with tumor necrosis and scar tissue, which is also a major impediment to drug development. Early measur- able surrogate end points rather than only survival are needed in clinical trials and daily practice. a Department of Clinical Neurosciences, Lausanne University Hospital, Rue du Bugnon 46, Lausanne 1011, Switzerland; b Department of Radiation Therapy, Lausanne University Hospital, Rue du Bugnon 46, Lausanne 1011, Switzerland; c Department of Medical Oncology, Lausanne University Hospital, Rue du Bugnon 46, Lausanne 1011, Switzerland * Corresponding author. Department of Clinical Neurosciences, Lausanne University Hospital (CHUV), Rue du Bugnon 46, Lausanne 1011, Switzerland. E-mail address: roger.stupp@chuv.ch KEYWORDS  PET  Brain tumor  Glioma  Neuro-oncology  Imaging KEY POINTS  Noninvasive imaging is essential for the precise diagnosis and follow-up of patients with brain tumors.  PET can play a key role in determining tumor aggressiveness, in determining the optimal biopsy site in low-grade glioma, and in differentiating tumor recurrence from treatment-induced alterations.  Validation of PET in prospective clinical studies is hampered by lack of reimbursement. For routine clinical use, these techniques would benefit from multicentric studies to establish the exact sensi- tivity and specificity of the methods, compared with the current standard practices.  PET imaging needs to be implemented in clinical pathways, and registries should accumulate evidences on whether it results in treatment modifications and improved patient outcome. To this aim, the help of regulating authorities and institutions is needed. PET Clin 8 (2013) 117–128 http://dx.doi.org/10.1016/j.cpet.2012.09.006 1556-8598/13/$ – see front matter Ó 2013 Elsevier Inc. All rights reserved. pet.theclinics.com