In a recent preclinical study, in vivo tumor targeting of a newly developed IDO1 tracer, 1-(2-[18F]-fluoroethyl)-L-tryptophan ([18F]FETrp), was compared with [11C] AMT and increased SUVs were observed for [18F] FETrp compared with [11C] AMT in lung, breast, and brain xenografts (Michelhaugh et al. 2017). Here, IDO1 is linked to neoplasm.