Imaging Proliferation in Lung Tumors with PET: 18F-FLT Versus 18F-FDG

Recently, the thymidine analog 3-deoxy-3-18F-fluorothymidine (FLT) was suggested for imaging tumoral proliferation. In this prospective study, we examined whether 18F-FLT better deter-mines proliferative activity in newly diagnosed lung nodules than does 18F-FDG. Methods: Twenty-six patients with pulmonary nodules on chest CT were examined with PET and the tracers 18F-FDG and 18F-FLT. Tumoral uptake was determined by cal-culation of standardized uptake value (SUV). Within 2 wk, pa-tients underwent resective surgery or had core biopsy. Prolifer-ative activity was estimated by counting nuclei stained with the Ki-67–specific monoclonal antibody MIB-1 per total number of nuclei in representative tissue specimens. The correlation be-tween the percentage of proliferating cells and the SUVs for 18F-FLT and 18F-FDG was determined using linear regression analysis. Results: Eighteen patients had malignant tumors (1