ESTABLISHMENT AND CLINICAL APPLICATION OF PROLIFERATION ACTIVITY AND MALIGNANT GRADE EVALUATION WITH POSITRON EMISSION TOMOGRAPHY.

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For the past two years, FLT-PET examination could be performed for 23 cases, including 12 cases of primary brain tumors. Patients, who gave informed consent, were given intravenous injection of FLT. Image of the brain was obtained 40 minutes later by 20-min emission scan and 3-min transmission scan. Region of interest was set on the tumor and semi-quantitative value of uptake (SUV) was measured and compared with histological diagnosis.Including prior cases, the clinical role of FLT-PET in the evaluation of malignant grade of primary brain tumors was investigated and reported in the paper as follows; 1) accumulation of FLT in the brain tumor reflected the malignant grade, 2) accumulation of FLT in the brain tumor correlated with the histological expression of Ki-67 which is a marker of cell proliferation, and 3) lesions with blood-brain barrier disruptions such as benign tumors and granuloma showed falsely increased FLT uptakes (Saga T, et al. Clin Nucl Med, 2006;31:774-80).In order to evaluate whether pretreatment FLT uptake can predict the prognosis of brain tumor patients, clinical status of brain tumor patients were followed. However, no correlation was observed between FLT uptake and duration of recurrence-free survival.In four patients who received FLT-PET examinations before and after treatment, change of FLT-uptake was compared with the clinical status of the patient. In two cases in which reduction of FLT uptake after treatment was low, early recurrences were observed for both patients. In two patients in which reduction rate of FLT uptake was high, although early recurrence was observed in one case, long-term recurrence-free survival was observed in the remaining case.In order to utilize the observed intratumoral distribution of FLT detected by FLT-PET to radiation treatment planning and determination of optimal biopsy site, image fusion of FLT-PET images was tried with corresponding CT or MRI images.