Analysis of 11c-methionine PET Uptake and Prognosis in Diffuse Gliomas According to the 2021 WHO Classification of CNS Tumors

Introduction: 11C-methionine PET is utilized in the preoperative evaluation of glioma patients. This study aimed to assess the correlation between 11C-methionine uptake, molecular features and prognosis in newly diagnosed diffuse gliomas.

Methods: 181 newly diagnosed glioma patients (Grade II: 25 patients, Grade III: 69 patients, Grade IV:87 patients according to the 2007 or 2016 WHO Classification) who underwent surgical resection at our hospital from 2000 to 2020 and imaged preoperatively using 11C-methionine PET were retrospectively included in this study. These patients were re-classified according to the updated 2021 WHO classification. The tumor-to-normal ratio (T/N) of 11C-methionine uptake was calculated by dividing the mean standardized uptake value (SUV) of the tumor by the mean SUV of the normal brain.

Results: Diffuse gliomas were re-classified into three categories according to the 2021 WHO classification: 26 oligodendrogliomas, IDH-mutant and 1p/19q-codeleted (grade 2:n=8, grade 3:n=18), and 29 astrocytomas, IDH-mutant (grade 2:n=7, grade 3:n=17, grade 4:n=5) and 88 Glioblastomas (=GBMs), IDH-wild type. GBMs included 6 molecular GBMs and 82 histological GBMs. 38 tumors were excluded from the analysis because they were re-classified as pediatric-type gliomas or did not fit any categories. In the same molecular categories, the methionine uptake increased for higher tumor grades. The median T/N ratios in oligodendrogliomas were 1.84 in grade 2 and 2.65 in grade 3, which were significantly higher than those in astrocytomas of the same grades (grade 2: 1.36, grade 3:1.65). The median T/N ratios for grade 4 gliomas were 2.22 in astrocytomas, 2.44 in molecular GBMs and 2.32 in histological GBMs with no significant differences among them. Kaplan–Meier survival analysis revealed that oligodendroglioma, IDH-mutant and 1p/19q-codeleted had significantly better outcomes regardless of WHO grade.

Conclusion : The results indicated that diffuse glioma categories reclassified with molecular classification correlate with both the T/N ratio of methionine uptake and the prognosis.