PROGNOSTIC VALUE OF POSITRON EMISSION TOMOGRAPHY WITH [F-18] FLUORO-2-DEOXY-D-GLUCOSE IN THE LOW-GRADE GLIOMA

OBJECTIVE: The natural history of the supratentorial low-grade glioma (LGG) of the adult is variable, and its malignant transformation is ha rdly predictable. Because positron emission tomography with [F-18]fluo ro-2-deoxy-D-glucose (FDG) has prognostic value in high-grade gliomas, this study was designed to search for a possible relationship between glucose metabolism and risk of malignant evolution in LGGs. METHODS: Positron emission tomography with FDG was performed in 28 patients wit h LGGs (22 at the time of diagnosis and 6 after the diagnosis). A meta bolic grading system based on the visual inspection of the positron em ission tomographic images was used. RESULTS: In 19 patients, no area o f FDC uptake higher than in the white matter was detected (metabolic G rade 1). All of those patients were alive at the end of the follow-up period. Only one of the patients presented a histological modification 7 months after the diagnosis. Nine patients presented areas of increa sed FDC uptake (metabolic Grade 2 or 3). Those areas were found in the tumor area in eight patients and in an area of radionecrosis in one. Of the nine patients with FDG ''hot spots,'' six died, two had recurre nce but were alive at the end of the follow-up period, and the patient with radionecrosis had no signs of recurrence. CONCLUSIONS: The prese nce of areas of increased FDC uptake in a histologically proven LGG pr edicts, in most cases, a deleterious evolution. This metabolic feature , detectable with a noninvasive procedure, may provide a clue to cellu lar changes, announcing malignant transformation in a tumor that retai ns the histological features of an LGG. Protocols with aggressive ther apeutic strategies in this situation should be considered for evaluati on.