Usefulness of (11)C-Methionine Positron Emission Tomography for Monitoring of Treatment Response and Recurrence in a Glioblastoma Patient on Bevacizumab Therapy: A Case Report

Recently developed molecular targeted therapies such as bevacizumab (BEV; Avastin) therapy have therapeutic efficacy for glioblastoma. However, it is difficult to distinguish between a tumor response and nonenhancing tumor progression with conventional magnetic resonance imaging (MRI) after BEV administration. Here we present a recurrent glioblastoma case in which (11)C-methionine positron emission tomography (MET-PET) provided useful information for detecting tumor recurrence after complete remission, as assessed by the Response Assessment in Neuro-Oncology criteria. A 47-year-old male with a left frontal lobe glioblastoma experienced recurrence 6 months postoperatively. We administered BEV concomitantly with temozolomide, subsequent to gamma knife surgery. Two months after starting BEV, complete remission was obtained. MET uptake on PET gradually decreased and had nearly disappeared 4 months after initiating BEV. No enhanced area was seen on MRI for 17 months after BEV initiation. Nevertheless, MET-PET revealed recurrence, visualized as nonenhancing tumor progression. MET-PET provides useful information for detecting glioblastoma recurrence, which lacks contrast enhancement on MRI after BEV therapy.