O-(2-18F-fluoroethyl)-L-tyrosine (18F-FET) PET as a potential selection tool for second surgery in glioblastoma patients.

BACKGROUND: Treatment-related changes still represent a diagnostic challenge in the management of patients with suspect of recurrent glioblastoma. The specificity of conventional MRI in detecting recurrence remains limited. Brain PET imaging provides information on tumor metabolism and can contribute to improving the diagnostic accuracy of cerebral neoplasms. We performed a retrospective analysis to evaluate the clinical value of O-(2-18F-fluoroethyl)-L-tyrosine (18F-FET) PET in the diagnosis of glioblastoma recurrence. METHODS: A retrospective analysis on patients considered suitable for salvage surgery for recurrence glioblastoma was performed. 18F-FET-PET was performed to investigate gadolinium enhancement suspected for recurrence. Static and kinetic 18F-FET parameters were analyzed and related to O-6-methylguanine-DNA methyltransferase (MGMT) status. RESULTS: Forty-two of the 51 patients who underwent 18F-FET-PET were re-operated. In each case, neuropathological diagnosis of tumor recurrence was confirmed. pMGMT hypermethylation was detected in 21 patients. Mean tumor-to-brain ratios (TBR) max was 3.87 (range 2.6-6.0). Static and kinetic 18F-FET parameters were similar according to MGMT status. CONCLUSIONS: 18FET-PET can be a reliable tool to improve the selection of patients suitable for salvage surgery for glioblastoma recurrence.

Current and future tools for determination and monitoring of isocitrate dehydrogenase status in gliomas.

PURPOSE OF REVIEW: Hotspot mutations of isocitrate dehydrogenase 1 (R132) or 2 (R172) genes affect 40% of diffuse gliomas, mostly grades II and III. The mutant enzyme produces high quantities of d-2-hydroxyglutarate (D2HG), which reshapes the epigenetic of the cell leading to gliomagenesis. For the clinician, the isocitrate dehydrogenase (IDH) mutation is a major biomarker with diagnostic, prognostic, and predictive consequences. With the development of specific inhibitors and vaccination, it appears also a potential actionable target. RECENT FINDINGS: IDH status is routinely determined on tumor sample by sequencing and immunohistochemistry detecting the most common mutant protein (IDH1R132H). Recently noninvasive diagnostic approaches have been developed based on the detection of the mutant DNA or the D2HG in body fluids, and the detection of D2HG by magnetic resonance spectroscopy of the brain. SUMMARY: These new techniques open avenues for non invasive diagnostic of glioma in patients not amenable to biopsy, in the preoperative setting and also duringpatients follow-up for evaluation of treatment response and prediction of recurrence.

Predictive biomarkers in adult gliomas: the present and the future.

PURPOSE OF REVIEW: This review summarizes recent studies on the predictive value of molecular markers in adult gliomas, including 1p/19q codeletion, MGMT methylation, IDH mutation and markers identified using omics and next-generation sequencing studies. RECENT FINDINGS: The long-term results of the Radiation Therapy Oncology Group and European Organization for Research and Treatment of Cancer trials in anaplastic oligodendroglial glioma have shown that the 1p/19q codeletion predicts an overall survival benefit from early PCV (procarbazine CCNU vincristine) chemotherapy. This benefit can also be predicted using gene expression-based molecular subtypes of gliomas while the predictive value of the IDH mutation in this context requires further study. In elderly patients with glioblastoma, the analysis of MGMT methylation status in two phase III trials suggests that this alteration may guide treatment decisions; however, this finding still needs confirmation in prospective studies. Omics and next-generation sequencing studies have identified additional potential predictive markers. In particular, IDH mutations, BRAF V600E mutations and FGFR gene fusions might predict efficacy of therapies targeted against these alterations. SUMMARY: Currently, the 1p/19q codeletion is the only well established predictive marker with clinical utility. However, it is likely that other molecular markers such as MGMT methylation, IDH mutation and those identified using omics and next-generation sequencing studies will further guide treatment decisions in adult gliomas.