THE USE OF PET IN EVALUATING PATIENTS WITH PRIMARY BRAIN-TUMORS - IS IT USEFUL

During an 18 month period 39 patients were evaluated with [F-18] fluor odeoxyglucose-PET (FDG-PET) for primary brain tumours. These included patients with suspected newly diagnosed tumours and patients with know n tumours who were being evaluated for possible recurrence or increasi ng tumour grade. Scans were performed on a 951-31 Siemen's PET scanner with 4 mm resolution. Scanning time was about 20 minutes per patient. Ah patients had undergone recent cerebral MRI. These patients were di vided into two groups. In the first group (30) MRI and PET concurred o n the diagnosis. The second group (nine) comprised those where the int erpretation of MRI and PET was different or there was a question of th e diagnosis on MRI. This group comprised three patients in whom MRI su ggested recurrent tumour and PET inaccurately suggested radiation necr osis; two patients with newly diagnosed enhancing lesions on MRI in wh om PET was useful in distinguishing strokes from tumour; two patients with prior gliomas with new enhancing isolated lesions on MRI in whom PET scan accurately depicted radiation necrosis; and two patients with newly diagnosed enhancing lesions on MRI in whom PET scan was helpful in distinguishing multiple sclerosis from tumour in one but not in th e other. Therefore, of the 39 patients, PET was helpful in five in dis tinguishing tumour from other disease processes; but, in so far as inf luencing treatment, it seemed helpful in only two. Thus PET seems to b e of limited value as an aid to evaluating and treating patients with suspected or known primary brain tumours.