title: Reliability of noncontrast-enhancing tumor as a biomarker of IDH1 mutation status in glioblastoma.
abstract: Isocitrate dehydrogenase 1 (IDH1) mutations in gliomas have been associated with a frontal lobe location and a greater proportion of noncontrast-enhancing tumour (nCET). The purpose of our study was to validate the utility of MRI imaging features in predicting IDH1 mutations in glioblastomas. Pre-operative MRIs of new glioblastoma patients, consisting of at least FLAIR and T1-weighted post-contrast sequences, were reviewed by a neuroradiologist based primarily on the VASARI feature set. IDH1 mutation testing was performed on all patients using immunohistochemistry. 153 patients met the inclusion criteria, of whom five had IDH1 mutations (3.3%). A frontal lobe location had equivalent frequency in both the IDH1-mutated and IDH1-wildtype cohorts (p=1.000). Three (60%) of the IDH1-mutated tumours had >33% nCET, compared to 21% of IDH1-wildtype (p=0.073). 12 tumours had a frontal lobe epicentre and >33% nCET, all being IDH1-wildtype. All five IDH1-mutated tumours had either a frontal lobe epicentre or >33% nCET, but none had both these features. Our results question the strength of the association between frontal lobe glioblastomas with substantial nCET and IDH1 mutations, as these features are also relatively frequent in IDH1-wildtype tumours, which are much more common. MRI is thus more useful for ruling out an IDH1 mutation rather than strongly suggesting its presence: if a particular glioblastoma does not have a frontal lobe epicentre and has less than 33% nCET, it can be predicted to be IDH1-wildtype with a high degree of confidence.
authors.affiliation: Department of Cancer Imaging, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia; Monash Imaging, Monash Health, Clayton, Victoria, Australia. Electronic address: arian.lasocki@petermac.org.
authors.forename: Arian
authors.initials: A
authors.lastname: Lasocki
authors.affiliation: Department of Pathology, The Royal Melbourne Hospital, Parkville, Victoria, Australia. Electronic address: alpha.tsui@mh.org.au.
authors.forename: Alpha
authors.initials: A
authors.lastname: Tsui
authors.affiliation: Department of Radiology, The Royal Melbourne Hospital, Parkville, Victoria, Australia; Department of Radiology, The University of Melbourne, Parkville, Victoria, Australia. Electronic address: frank.gaillard@mh.org.au.
authors.forename: Frank
authors.initials: F
authors.lastname: Gaillard
authors.affiliation: Melbourne EpiCentre, Department of Medicine, The University of Melbourne, Parkville, Victoria, Australia; Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Victoria, Australia. Electronic address: mark.tacey@monash.edu.
authors.forename: Mark
authors.initials: M
authors.lastname: Tacey
authors.affiliation: Department of Neurosurgery, The Royal Melbourne Hospital, Parkville, Victoria, Australia; Department of Surgery, The University of Melbourne, Parkville, Victoria, Australia. Electronic address: kate.drummond@mh.org.au.
authors.forename: Katharine
authors.initials: K
authors.lastname: Drummond
authors.affiliation: Monash Imaging, Monash Health, Clayton, Victoria, Australia; Departments of Medicine and Imaging, School of Clinical Studies at Monash Health, Monash University, Clayton, Victoria, Australia. Electronic address: stephen.stuckey@monashhealth.org.
authors.forename: Stephen
authors.initials: S
authors.lastname: Stuckey
mesh_terms: D000328:Adult; D015415:Biomarkers; D014408:Biomarkers, Tumor / Q000235:genetics*; D001932:Brain Neoplasms / Q000000981:diagnostic imaging* / Q000235:genetics*; D005260:Female; D005909:Glioblastoma / Q000000981:diagnostic imaging* / Q000235:genetics*; D006801:Humans; D007521:Isocitrate Dehydrogenase / Q000235:genetics*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D009154:Mutation / Q000235:genetics; D015203:Reproducibility of Results
chemical_list: D015415:Biomarkers; D014408:Biomarkers, Tumor; D007521:Isocitrate Dehydrogenase; C543588:IDH1 protein, human
keywords: Glioblastoma; Isocitrate dehydrogenase; Magnetic Resonance Imaging; Noncontrast-enhancing tumour