Hypoxia and positron emission tomography in patients with gliomas

Purpose The treatment of brain tumors poses a challenge for the medical community and is an interdisciplinary endeavor. Especially tumor cells of high-grade gliomas are able to develop chemo-and radioresistance. One of its key causes is known to be hypoxia. In the last two decades, positron emission tomography (PET) with tracers like [18F] fluoromisonidazole has become established to visualize hypoxic subvolumes, offering new treatment approaches for the radio-oncologist. This review is meant to summarize the association between the hypoxic subvolume in patients with glioma and clinical and histopathological parameters, while pointing out the challenge of using this knowledge to improve patient outcome from a radio-oncological perspective. Methods We searched the PubMed database for the terms "brain tumor'', "hypoxia'' and "PET'', as well as "brain tumor'', "hypoxia'' and "radiotherapy''. Results In the end we found 13 studies dealing with hypoxia PET-tracers in humans with glioma. The hypoxic volume (HV) is associated with higher tumor grade and poor prognosis and it seems to overlap to some extent with the contrastenhanced volume in magnetic resonance imaging. Conclusion Hypoxia visualized by PET in patients with glioma indicates poor prognosis. Before HV can be specifically targeted by radiation therapy further studies are needed.