Prognostic effects and correlation of molecular markers with previous histopathological diagnosis for grade 2 and 3 gliomas

Background: Recently, new molecular markers have been identified after analysis of genetic mutations of glial tumors and these molecular markers have been included in the new diagnostic algorithm with "WHO 2016 Brain Tumors Classification". In our study, we aimed to demonstrate the changes in Grade 2 and 3 glial tumors after a new pathologic classification. Methods: After the approval of the Clinical Research Ethics Committee of the Akdeniz University Medical Faculty, patients who underwent surgery in neurosurgery department have pathologic Grade 2 and 3 glial tumors pathology were included in the study. Previous histopathological preparations were reassessed and IDH mutations were detected by real time PCR and 1p/19q codeletions were detected by FISH (Fluorescent In Situ Hybridization). Once the genetic markers were identified, the diagnoses were re-diagnosed according to WHO 2016 Brain Tumor Classification and the results of the new diagnoses were analyzed. Karnofsky performances score (KPS), Ki-67 proliferative, glioma associated seizure rates, tumor localizations, IDH and 1p/19q codeletion status, surgical type and postoperative adjuvant therapies were evaluated in addition to the survival outcomes of the patients after the new diagnostic group analysis. Results: We studied 13 (15.7%) oligodendendrogliomas, 41 (49.4%) astrocytomas and 29 (34.9%) oligoastrocytomas patients with previous histopathological diagnosis group. The average age of all patients was 42.41. Of the patients, 54 (65%) were male and 29 (35%) were female. IDH mutation was detected in 51 (62%) of the patients after genetic analysis, whereas 1p/19q codeletion was detected in 20 (24%) patients. Glioma-associated seizures were found in 30 (62%) of IDH mutation-positive patients (p= 0.03). After analysis of the molecular markers, 20 (24.1%) patients were assigned to IDH mutation 1p/19q codel oligodendroglioma, 31 (37.3%) patients IDH mutant astrocytoma and 32 patients (38.6%) IDH wt astrocytoma diagnostic groups. IDH wt astrocytomas have the worst prognostic group among all diagnostic groups. It was observed that Ki-67, tumor localization, IDH and 1p/19q status, surgical type and postoperative adjuvant treatments had statistically significant effects on survival outcomes. Conclusion: Grade 2 and 3 gliomas were separated into more homogeneous diagnostic groups for survival after entering molecular markers into diagnostic algorithms. The grading system, formerly called histopathologic examination, continues to be important in other diagnostic groups, although it is not prognostic for overall survival in IDH wt gliomas. Patients who do not receive appropriate treatment due to their previous diagnosis, will increase their survival after layered diagnosis.