Abstract
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Objectives 4'-[methyl-11C]-thiothymidine (4DST) has been developed as an in vivo cell proliferation marker based on the DNA incorporation method. We evaluated 4DST uptake in patients with newly diagnosed gliomas and correlated the results with tumor grade and proliferative activity, in comparison with 11C-methionine (MET).
Methods Nineteen patients with newly diagnosed gliomas were examined with 4DST PET and MET PET. PET imaging was performed at 15 min after each radiotracer injection. Tumor lesions were identified as areas of focally increased uptake, exceeding background uptake in the brain. For semi-quantitative analysis, the standardized uptake value (SUV) was determined by region-of-interest analysis. The maximal SUV (SUVmax) for tumor (T) and the mean SUV for contralateral normal brain tissue (N) were calculated and T/N ratio was determined. Metabolic tumor volume (MTV) was also determined as the volume of tumor showing uptake. Tumor grading and proliferative activity as indicated by the Ki-67 index were estimated in tissue specimens.
Results The sensitivity of 4DST PET and MET PET for the detection of newly diagnosed gliomas was 89% and 100%, respectively. There was a significant difference in SUVmax on 4DST PET between gliomas of grades II and IV (p<0.05). There was a correlation between SUVmax (r=0.47; p<0.04), T/N ratio (r=0.45; p<0.05) and MTV (r=0.51; p<0.03) on 4DST PET and Ki-67 index. There was no significant difference between each value on MET PET and tumor grade and Ki-67 index.
Conclusions The results of this preliminary study suggest that, compared with MET PET, 4DST PET seems to be useful in the noninvasive assessment of grade and proliferation in newly diagnosed gliomas.