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ON THE BIOLOGICAL BEHAVIOUR AND PROGNOSIS OF ANAPLASTIC OLIGODENDROGLIOMA WITH NECROSIS Free

INTRODUCTION: Previously we have shown that glioblastomas with an oligodendroglial component (GBMO) did not differ from other glioblastomas in the frequency of 1p/19q deletion or isocitrate dehydrogenase mutation. Here we seek to determine whether anaplastic oligodendrogliomas with necrosis and very prominent endothelial cell hyperplasia (AO + N), often diagnosed as GBMO, differ in prognosis from the classic grade III counterpart (AOIII) and GBMO. METHOD: Anaplastic oligodendrogliomas with 1p/19q co-deletion and mutation to IDH1 or IDH2 were classed as either grade III or IV dependent upon the presence of the above mentioned high grade features. GBMO with neither 1p/19q co-deletion nor mutation to IDH1 or IDH2 were also selected for comparison. Statistical analyses were performed using R-Stats v2.15.2. RESULTS: AO + N (n = 16) with a median survival of 66.5 months had a worse prognosis than AOIII (n = 30) (median not reached, p = 0.04) and a better prognosis than GBMO (n = 46) (median survival 9 months, p = 1.04X10-5). The difference in survival between AO + N and GBMO remained significant when adjusted for age and gender (HR 0.17 95% CI 0.07-0.4, 6.3X10-5). CONCLUSION: The results suggest that anaplastic oligodendroglioma with necrosis and prominent endothelial cell hyperplasia behave worse than classic anaplastic oligodendroglioma and better than GBMO. Proper consideration should be given to including these neoplasms as a novel WHO grade IV classification if these results can be replicated in a larger cohort.