10181- NI-14 RELATIONSHIP BETWEEN METHIONINE PET FINDINGS AND CLINICAL AND MOLECULAR PATHOLOGICAL FEATURES IN BRAIN TUMORS

Abstract INTRODUCTION The usefulness of methionine PET scan in the diagnosis of brain tumors is widely recognized, and it is frequently used to distinguish nonneoplastic lesions in primary tumors and radiation necrosis in recurrent lesions. It is also useful in surgery to identify the extent of resection due to its ability to be taken up by actively dividing tumor cells. METHODS We retrospectively analyzed electronic medical records and genetic analysis data of 744 consecutive patients who underwent methionine PET examination at our department from February 2019 to April 2023. During this period, tumor cases and suspected tumor cases were basically included in the study. RESULTS There were 34 cases in which the pathological diagnosis of the excised specimen was “tumor” despite the absence of significant methionine accumulation. These included astrocytoma WHO Grade 2, cavernous hemangioma, and spinal ependymoma. On the other hand, 44 patients with a final diagnosis of “non-neoplastic disease” showed methionine accumulation. All patients with Glioblastoma and Oligodendroglioma were MET-PET positive, while 18 of 46 patients with Diffuse astrocytoma did not show methionine accumulation. Diffuse astrocytoma without methionine uptake tended to have better O S and P F S than those with methionine uptake. CONCLUSION Methionine PET is useful for the diagnosis of neoplastic disease, but it should be used with caution, especially in astrocytomas, because some cases were found to have no uptake, and a certain number of non-tumor cases were found to have uptake. In the treatment of patients with astrocytoma, data integration with intraoperative MRI and intraoperative molecular analysis techniques may improve the accuracy of surgery, and we report an actual case.