NI-10 Reclassification of diffuse gliomas based on molecular diagnosis -evaluation of methionine uptake and treatment outcome-

Object: The revised 2016 WHO Classification of Tumours of the Central Nervous System incorporates genetic alterations into the classification system, with the goal of creating more homogenous disease categories with greater prognostic value. In this study, we reclassified diffuse gliomas with molecular diagnosis and examined for 11C-methionine uptake and prognosis. Methods. 182 diffuse glioma patients (Grade II in 42 patients, Grade III in 61 patients, Grade IV in 77 patients) treated at Tokyo Medical and Dental University Hospital from 2000 to 2018 were included in this study. The IDH1/2, ATRX and 1p19q status were analyzed using tumor samples. The tumor-to-normal ratio (T/N) of 11 C-methionine uptake was calculated by dividing the mean standardized uptake value (SUV) for the tumor by the mean SUV of the normal brain. Result. By molecular diagnosis, 11 diffuse astrocytomas and 17 anaplastic astrocytomas were diagnosed as “IDH-mutant”, while 14 diffuse astrocytomas and 29 anaplastic astrocytomas were diagnosed as “IDH-wild”. 5 out of 77 grade IV tumors had IDH mutation. 4 tumors were diagnosed as “Diffuse midline glioma, H3 K27M-mutant”. In the 32 oligodendroglial tumors, 12 oligodendrogliomas and 9 anaplastic oligodendrogliomas were diagnosed as “IDH-mutant and 1p/19q-codeleted”. The median T/N ratios in oligodendroglial tumors with “IDH-mutant and 1p/19q-codeleted” were significantly higher than those in astrocytic tumors with “IDH-mutant”. On the other hand, in tumors with the same genetic background, higher grade tumor has significant higher T/N ratio. Kaplan-Meier survival analysis revealed that oligodendroglial tumors with “IDH-mutant and 1p/19q-codeleted” had significantly better outcomes regardless of WHO grade. Overall survival was 90.9% at 5 years and 77.9% at 10 years in oligodendroglial tumors with “IDH-mutant and 1p/19q-codeleted”. IDH wild tumors had significantly worse outcomes.Conclusions. The results indicated that diffuse glioma categories reclassified with molecular classification correlate with the T/N ratio of methionine and the prognosis.