Kinetics of 39-Deoxy-39-18F-Fluorothymidine During Treatment Monitoring of Recurrent

39-deoxy-39-18F-fluorothymidine (18F-FLT) is usedasabiomarker of cell proliferation. We investigated the kinetics of 18F-FLT dur-ing treatment of malignant glioma with bevacizumab and irinote-can. Methods: Fifteen patients with recurrent high-grade brain tumors (2 grade III, 13 grade IV) were studied at baseline (study 1 [S1]), after 1 course of therapy (2 wk, study 2 [S2]), and at the end of therapy (6 wk, study 3 [S3]). 18F-FLT (1.5 MBq/kg) was administered intravenously, and dynamic PET was performed for 1 h. Curves representing blood clearance and tumor uptake were derived from factor images and summed frames with thresholding techniques or with a fixed cube. The standard 18F-FLT model was used to estimate the rate constants. 18F-FLT uptake was measured at 2 time points (early standardized uptake value [SUVearly] and late SUV [SUVlate]). Results: Param-eters appeared similar for curves derived from factor images an