PATH-10. PROGNOSTIC RELEVANT IMMUNOPHENOTYPES OF PEDIATRIC HIGH-GRADE NON-BRAINSTEM GLIOMAS

Pediatric diffuse astrocytomas comprise a wide range of malignancies with variable prognosis. The 4(th) grading system used now not always correctly characterizes the biological behavior of these tumors. We collected 24 pediatric supratentorial non-brainstem high grade glioma cases. Patient age ranged from 1 to 18 years old (median 11y). Main tumor locations were as follows: parietal lobe 8 cases; temporal lobe, 10 cases; frontal lobe, 3 cases; occipital lobe 3 cases. Eight of them were totally removed. All patients were treated with standard CT and RT. The main objective was to assess the prognostic impact of histopathological and molecular criteria on progression‐free(PFS) and overall survival (OS) of high grade gliomas. The following criteria were analyzed: IDH1 R132H, BRAF V600E expression, ALT-phenotype, CDKN2A deletion, 1p/19q co-deletion, glial and neuronal markers expression. RESULTS: IDHR132H mutation was identified in 3 cases. 4 cases carried BRAFV600E mutation with CDKN2A deletion and displayed PXA phenotype. 5 cases showed undifferentiated glial morphology and ALT–phenotype. Also there was a group of tumors without any of the above mentioned genetic changes. Interestingly 3 of them were post radiation tumors. Statistical analysis showed that low OS correlated with ALT-phenotype(p-0.015), absence of neuronal markers expression and absence of molecular changes (p-0.03). Mutation of IDH1R132H was a favorable prognostic factor as in the adult population. PFS was affected only by the presence of neuronal expression (p-0.015). Employing immunohistochemical analysis with surrogate molecular markers in complex with FISH can provide additional prognostic information in case of pediatric high grade gliomas.