Functional and molecular imaging in cancer drug development
Imaging biomarkers have a potential to identify key metabolic pathways that are up-regulated in cancer cells compared to normal cells. In early drug development, they can provide valuable information on the dissemination of the drug and estimate whether the drug reaches the target and, consequently, to determine the appropriate clinical benefit. The use of imaging as an early surrogate biomarker of response is also appealing, since it allows to tailor treatment regimens in individual patients. The aim of this review is to describe various imaging biomarkers covering most important cancer hallmarks such as cell death, proliferation, metabolism, vascularity, and hypoxia. We highlight the current status of using molecular imaging such as fluorodeoxyglucose (FDG), fluorothymidine (FLT), fluoromisonidazole (FMISO), and fluoroazomycin arabinoside (FAZA) positron emission tomography (PET) as well as advanced magnetic resonance imaging (MRI) techniques such as dynamic contrast enhancing (DCE) and diffusion weighted (DW)-MRI, and their potential roles in cancer drug development.