GE-08 * TARGETED NEXT GENERATION SEQUENCING OF ARCHIVAL FFPE SAMPLES FROM EORTC STUDY 26951 SHOWS STRONG PROGNOSTIC VALUE OF A MOLECULAR CLASSIFICATION IN LOCALLY DIAGNOSED GRADE III OLIGODENDROGLIOMA

BACKGROUND: Molecular holds promise for an improved classification of glial tumors. We analyzed samples of patients enrolled in EORTC study 26951 on adjuvant PCV in anaplastic oligodendroglial tumors to evaluate 1. The clinical significance of glioma classification with Next Generation Sequencing (NGS); and 2. The prognostic significance of CIC and FUBP mutations. MATERIAL AND METHODS: EORTC 26951 investigated adjuvant PCV in locally diagnosed anaplastic oligodendroglial tumors. NGS was performed on archival formalin fixed paraffin embedded (FFPE) samples using the Ion Torrent Personal Genome Machine for simultaneous detection of mutations in the genes for ATRX, CIC, EGFR, FUBP1, NOTCH1, PTEN, and TP53 and hot spot mutation regions in BRAF, H3F3A, IDH1, IDH2 and PIK3CA as well as imbalances on chromosome 1p, 10q, 7 en 19q. TERT mutations were assessed with PCR. RESULTS: At the time of abstract submission 89 cases have been investigated, more samples are being processed. In 62 tumors an IDH1 mutations was found, in 2 an IDH 2 mutation. Forty-eight tumors (54%) were 1p/19q codeleted, 29 (60%) of these had CIC mutations and 20 (42%) had FUBP mutations. All but one 1p/19q codeleted tumors showed TERT mutations. Ten tumors showed ATRX mutations, 5 also had PTEN mutations. Median OS was 136 months for CIC mutated 1p/19q co-delete tumors, and 95 months for CICwt tumors (p = 0.17); FUBP mutations showed no relation with OS. TERT mutations were found in 60 tumors (67%), OS in TERT mutated but 1p/19q intact tumors was 12 months. IDH mutations, TERT mutations and 1p/19q co-deletion were the most significant prognostic factors, distinguishing between groups with significantly different OS. CONCLUSIONS: The ongoing expansion of this series will show if CIC mutations have prognostic significance. Targeted NGS even on archival FFPE allows a clinically relevant prognostic classification of glioma, while simultaneously identifying relevant druggable targets.