HGG-53. "Profile of High Grade Gliomas and Diffuse Intrinsic Pontine Gliomas in Greek Pediatric Patients: an 8-year Single Institution's experience"

BACKGROUND/OBJECTIVES: Aggressive clinical and biological behavior, high morbidity and mortality are the main characteristics of pediatric high-grade-gliomas (HGG). Our aim was to study patients (pts) with ΗGG or diffuse-intrinsic-pontine-glioma (DIPG), diagnosed in the largest pediatric neurooncology Center in Greece. DESIGN-METHODS: We performed a retrospective-review of newly-diagnosed pts with HGG or DIPG during 2014-2021. Gender, age, location, resectability, type of surgery, histological and molecular characteristics, management and outcome were analyzed. RESULTS: During the study-period, 38pts (18females), median age:9.35y(range:3days-16.9y), were diagnosed in our center. The most common tumor-location were pons (17/38 pts) and parietal lobe (11/38 pts). DIPG based on imaging-studies was diagnosed in 16pts. Surgical approach was performed in 32pts (VP-shunt insertion:8, biopsy:12, partial resection:6, subtotal: 6). In 23pts(5 brainstem-tumors) a histological-diagnosis was feasible. Astrocytoma grIV was found in 60.8% and grΙΙΙ in 26.1%(14 and 6 respectively). Of notice, 3 additional pts with histological findings of low-grade(2grII and 1gr1), were upgraded in grIV after molecular-studies and DNA-methylation analysis. Furthermore, 17.3% of the pts (4/23, 3 located in the midline) carried a Η3Κ27Μ-mutation (diffuse midline glioma, DMG), 17.3% a Η3F3A-mutation and 8.6% showed ΕGFR-overexpression. All patients>3years of age were treated upfront according to HIT-HGG2013 with radiotherapy-temozolomide (29/32pts). In 5DIPG pts, reirradiation after disease-progression resulted in temporary symptomatic improvement. HGG-pts upon progression were treated with bevacizumab-irinotecan. Of the 38pts, 6pts elected to receive treatment in other countries. Overall-survival was 75.1%,15.1% and 3.7% at 1,2 and 3 years post-diagnosis respectively. Patients with DIPG/ DMG and non-midline HGG had a median overall-survival of 1.10 years and1.34 years, respectively. CONCLUSIONS: The experience of our unit concurs with worldwide published series and shows that pediatric HGG and DIPG have a dismal prognosis. Re-irradiation may offer short survival prolongation. ASKNOWLEDGEMENTS: Authors asknowledge the contribution of KiTZ-Heidelberg in molecular diagnostics through collaboration with ACCC.