PET biomarkers and probes for treatment response assessment in glioblastoma : a work in progress

Aims: Several pharmacological approaches are used for glioblastoma (GBM) treatment, each hinging on the triggering of different biochemical or functional processes; the development of specific and sensitive PET procedures for monitoring their efficacy proceeds with the identification of such new treatments. This paper presents an overview of the available “tumour biomarker”–“PET probe” pairs (i.e. the combination of a tumour target and a selective PET radiopharmaceutical) for monitoring the different treatments for GBM tested in human subjects. Methods: A bibliographic search for papers on PET imaging for assessing treatment response in GBM was performed in PubMed and Web of science databases using the following string: (PET or positron) and (glioblastoma) and (treatment) and (monitoring); papers dealing with studies in human subjects published over the last 10 years were reviewed. Further papers were extracted from the bibliography of the reviewed papers. Results: In this review, we highlight through a detailed table that in spite of the current use in GBM patients of a large variety of PET radiopharmaceuticals, very few papers have specifically addressed the issue of the optimization and use of imaging biomarker–probe pairs for the assessment of treatment response in GBM. While new PET probes are being developed for assessing old and new GBM biomarkers, very few clinical trials have been performed to this end. Conclusion: Whereas it appears that the use of old and new PET radiopharmaceuticals can advance the non-invasive assessment of treatment response in GBM, the optimal match of biomarker–probe pairs although highly needed is still being sought in particular with the active development of new highly specific treatments characterized by novel antitumoral targeting strategies.