NIMG-30. PREOPERATIVE PREDICTORS OF MALIGNANCY IN NON-ENHANCING GLIOMA IN THE ERA OF MOLECULAR CLASSIFICATION

• Published in: Neuro-oncology (Charlottesville, Va.) Va.), 2018-11, Vol.20 (suppl_6), p.vi182-vi182
• Main Authors: Dao Trong, Philip, Jesser, Jessica, von Deimling, Andreas, Kilian, Samuel, Herold-Mende, Christel, Unterberg, Andreas, Jungk, Christine
• Format: Article
• Language: English
• Subjects: Abstracts
• ISSN: 1522-8517; 1523-5866
• DOI: 10.1093/neuonc/noy148.756

Abstract INTRODUCTION The association of contrast enhancement with malignancy in glioma is widely accepted. A higher grade of uncertainty exists for preoperative grading of non-enhancing tumors. Here, we sought to reevaluate tumor grading of non-enhancing glioma with the new WHO classification of 2016 and analyzed clinical data and radiographic features (T2/FLAIR mismatch sign, subventricular zone involvement, tumor volume and growth) which might predict WHO grading, IDH mutation or PFS. METHODS Out of 626 glioma patients, 72 with non-enhancing glioma underwent supratentorial surgery in our department (2012 – 2017). Median follow-up was 24.5 months. Histopathological and molecular examinations were performed by our neuropathologists in concordance with the 2016 WHO classification. The “T2/FLAIR mismatch sign” and tumor involvement with the subventricular zone were evaluated by two independent investigators. Medical records of all patients were reviewed. The “Pignatti” score was calculated as previously described. RESULTS 57% (41) of patients were IDHmut, 43% (31) IDHwt. 75% of the total study cohort (54 patients) in which preop-MRI suggested low grade glioma, were classified grade III or IV and thus considered malignant. Involvement of the subventricular zone correlated with PFS (log-rank p= 0.02). Age significantly correlated with PFS (log-rank p= 0.01) and with tumor grade (log-regression p< 0.001). When applying the new WHO classification to the Pignatti score, no correlation in PFS and tumor grading could be seen. The T2/FLAIR mismatch sign was confirmed to be highly specific for IDH mutation (positive predictive value 96%). CONCLUSION 75% of non-enhancing suspected low grade glioma were indeed grade III or IV according to the new WHO classification of 2016. We confirmed the T2/FLAIR-mismatch sign to be a highly specific marker for IDH mutation and found that involvement of the tumor with the subventricular zone was significantly correlated with worse PFS. These results may help to improve preoperative patient counseling.