gms | German Medical Science

Objective: WHO grade III glioma comprise a genetically heterogeneous group of Oligodendrogliomas characterized by the co-occurrence of the IDH mutation and 1p19q co-deletion and Astrocytomas with or without IDH-mutation. Most of these tumors display a rather benign clinical course, but especially IDH1/2 wild-type astrocytomas have a worse prognosis similar to glioblastomas. Epileptic seizures are the most common symptom at the time of initial diagnosis and, presence of seizures seems to be relevant for prognosis, especially in glioblastomas. Our study investigates the occurrence of epileptic seizures in WHO grade III gliomas at the time of initial diagnosis and their impact on overall prognosis.

Methods: We included a cohort of 110 histopathologically and molecularly stratified WHO°III gliomas. Tumor volume was quantified by tumor segmentation of preoperative FLAIR as well as contrast enhancing MRI sequences. Segmentation was performed by OSIRIX-software. The occurrence of epilepsy was extract ed from clinical documentation based on EEG Data.

Results: In our cohort, 32 patients were diagnosed with an oligodendroglioma, 21 patients with an IDH1/2 mutated astrocytoma and 56 with an IDH wildtype astrocytoma. The occurrence of seizures was common but similar distributed in all subgroups (oligodendroglioma 71.8%, astrocytoma IDH mutated 71.4% and astrocytoma IDH wildtype 68%, p>0.05). No significant correlation of seizures and tumor volume could be detected (OR 0.9, p>0.05), in addition, the distribution of tumor volumes was the same in all molecular subgroups (p>0.05.) In Cox-regression analysis, we could detect a significant benefit for patients that suffer from seizures (median OS 3.6 years) in contrast to patients without seizures seizures (median OS 1.8 years; HR 0,56. p=0.02). Next, in a multivariate analysis, we identified the presence of seizures at the time of initial diagnosis and the molecular stratification as the only independent prognostic factors for WHO grade III glioma.

Conclusion: In summary, we have identified the presence of epilepsy as the most important prognostic factor across all molecular subgroups in the WHO grade III gliomas. Similar results have been reported for glioblastomas, but the mechanism for improved survival promoted by seizures is poorly understood. These findings encourage further investigations of the underlying differences in gliomas with or without seizure activity, which may provide interesting better prognostic evaluation and help in clinical decision making.