Methyl-l-¹¹C-Methionine PET as a Diagnostic Marker for Malignant Progression in Patients with Glioma

¹¹C-MET PET of 39-y-old man with malignant progression of recurrent glioma. (A) Newly diagnosed grade II astrocytoma with average ¹¹C-MET uptake of 1.3 to contralateral gray matter, with no enhancement on contrast-enhanced CT and no immunohistochemical VEGF expression. (B) One year later, patient presented with malignant progression to grade III astrocytoma associated with significant increase in ¹¹C-MET uptake (to 2.1-fold) and only slight contrast enhancement outside metabolically active tumor. Histologic analysis from resection showed increase in cellularity, numerous pleomorphic nuclei, and low VEGF expression. (C) In following year, resection of tumor again confirmed malignant progression to glioblastoma multiforme, showing markedly increased uptake of ¹¹C-MET (to 2.8-fold), marginal contrast enhancement on MRI, and ∼35% of tumor cells expressing VEGF (original magnification, ×400). PET-guided biopsies were taken from region with highest ¹¹C-MET uptake, which was in different locations within same tumor over time.