Thymidine phosphorylase influences [ 18 F]fluorothymidine uptake in cancer cells and patients with non-small cell lung cancer

Purpose Thymidine phosphorylase (TP), a key enzyme in the pyrimidine nucleoside salvage pathway, catalyses the reversible phosphorylation of thymidine, thereby generating thymine and 2-deoxy-D-ribose-1-phosphate. By regulating the levels of endogenous thymidine, TP may influence [18F]fluorothymidine ([18F]FLT) uptake. We investigated the effect of TP activity on [18F]FLT uptake by tumours.