[Treatment of brain tumors investigation by positron emission tomography]

The effects of glucocorticoids (GC) on the blood-to-tumour barrier transport (BTT) and tissue blood volume (Vb) and aspects of brain tumour acid/base balance were studied in patients with brain tumours using positron emission tomography (PET). BTT was assessed by 82Rb/PET and quantitated as K1 (unidirectional transport constant), tissue blood volume was also measured by 82Rb/PET. The parameters were evaluated following start of GC. The pH was assessed with 11C-DMO/PET as a single measurement in patients receiving GC. GC treatment reduced the tumour K1 20% to 30%, within 6 to 24 hours following start of treatment. Brain tumours were in the alkalotic range compared to normal brain. The studies have helped to explain GC's antioedema effect and mechanisms behind the observed tumor alkalosis. The 82Rb/PET model seems useful for quantitative measurements of such parameters as pharmacological blood-tumour barrier opening, allowing continuous assessment of the potential for tumour chemotherapeutic uptake, thereby improving anti-cancer chemotherapy.