NI-06 MOLECULAR DIAGNOSIS, 11C-METHIONINE UPTAKE AND PROGNOSIS IN GRADE 2 AND 3 GLIOMAS

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 103 consecutive lower grade gliomas using the revised 2016 WHO classification and examined for 11C-methionine uptake and prognosis.

103 consecutive lower grade glioma patients (Grade 2 in 41 patients, Grade 3 in 62 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 maximum standardized uptake value (SUV) for the tumor by the mean SUV of the normal brain.

In the integrated diagnosis, 11 astrocytomas and 17 anaplastic astrocytomas were diagnosed as “IDH-mutant”, while 14 astrocytomas and 29 anaplastic astrocytomas were diagnosed as “IDH-wild”. In the 32 oligodendroglial tumors, 12 oligodendrogliomas and 9 anaplastic oligodendrogliomas were diagnosed as “IDH-mutant and 1p/19q-codeleted”. The concordance rate with 1p19q co-deletion and ATRX retention was 94.7%. The median T/N ratios in oligodendroglial tumors with “IDH-mutant and 1p/19q-codeleted” were 1.83 in Grade 2 and 2.83 in grade 3, which were significantly higher than those in astrocytic tumors with “IDH-mutant” (G2: 1.38, G3:1.62). 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”.

The results indicated that lower grade glioma categories reclassified with molecular classification correlate with the T/N ratio of methionine and the prognosis.