LGG-03. INCIDENCE AND OUTCOME OF PEDIATRIC IDH-MUTANT GLIOMA

INTRODUCTION: The incidence of IDH mutations in pediatric glioma is unclear. Recent publications suggest rates ranging between 0–20%. Therapy poses challenges as it is unclear if the biology and prognosis of pediatric IDH-mutant gliomas are identical to adults. METHODS: We performed an IRB approved, systematic retrospective search for IDH-mutant gliomas in the Dana-Farber Cancer Institute/Boston Children’s Hospital database between 2009–2018, analyzing incidence, demographics, histology, co-occurring genetic alterations and outcome. RESULTS: We identified 575 patients with glioma, ages 0–21 years. Of these, 394 underwent biopsy/resection (0–9 years:n=204; 10–21 years:n=190), with 294 genetic testing. Fifteen of 294 tumors (5%) were IDH1-mutant. Among patients 0–9 years and 10–21 years, 1/156 (0.6%) and 14/138 (10%) had IDH1-mutant tumors, respectively. Among patients 10–21 year old, 13/115 low-grade gliomas were IDH1-mutant (11%). High-grade gliomas accounted for the remaining 23, with one IDH1-mutant glioma (4%). Most common co-occurring genetic alterations for diffuse astrocytoma (n=12) were TP53 (n=9) and ATRX (n=2). Three patients with IDH1-mutant oligodendrogliomas had 1p/19q deletion. Eleven IDH1-mutant patients were evaluable for outcomes with median follow-up of five years. Five-year radiation-free, progression-free and overall survival for patients with low-grade histology were 76% and 100%, respectively. One patient with high-grade glioma recurred 1.2 years after upfront chemo-radiation and died soon after recurrence. CONCLUSION: IDH-mutant gliomas comprise a small proportion of pediatric gliomas. Incidence rate is higher in the second decade of life. Comparative analyses between pediatric IDH-mutant gliomas and adult historical cohorts are currently underway, evaluating outcomes, radiation therapy and frequency of malignant transformation.