FDG-PET as a prognostic factor in high-grade astrocytoma

Background: The prognostic value of the metabolic status of cerebral glioma s determined by positron emission tomography with [F-18]-fluoro-deoxy-D-glu cose (FDG-PET) has been established in populations with a mixture of grades 2, 3 and 4 gliomas, but remains uncertain when only malignant gliomas are considered (grade 3 and 4). Methods: FDG-PET performed in 30 patients with anaplastic astrocytoma (grad e III) and 61 patients with glioblastoma (grade 4) were classified accordin g to a metabolic grading. The uptake of FDG was lower in the tumor compared to white matter (WM) in grade 1 (4 glioblastoma, 4 anaplastic astrocytoma) , it was intermediate between WM and cortex in grade 2 (20 glioblastoma, 22 anaplastic astrocytoma), and it was superior to cortex in grade 3 (38 glio blastoma, 4 anaplastic astrocytoma). Results: Kaplan-Meier survival curves were similar in patient with grades 1 and 2, but were significantly worse (p = 0.007) in grade 3. In multivariat e analysis considering age, pathological grade (anaplastic astrocytoma vers us glioblastoma), and metabolic grades, the metabolic grade did not appear to be an independent prognostic factor. When anaplastic astrocytomas and gl ioblastomas were considered separately, metabolic grade is of predictive va lue only in the group of glioblastomas. Conclusion: In malignant gliomas, metabolic grading determined by FDG-PET w as not superior to the pathological grading for survival prediction. Still, it remains of predictive value when applied to malignant gliomas histologi cally classified as glioblastoma.