RecruitingEarly Phase 1Drug trialUsing a PET Imaging Agent, 18F-Clofarabine (CFA), to Measure Deoxycytidine Kinase Activity in Metastatic CancerThe purpose of this study is to evaluate whether a new type of imaging study, called 18F-Clofarabine (CFA) PET/CT, can be used to image cancer pyrimidine metabolism in participants. PET (positron emission tomography) imaging is a way of looking at cancers that can reveal cancer metabolism. Presently, however, there are no imaging agents in routine use to look at an aspect of cancer metabolism (pyrimidine metabolism) that dictates whether certain cancer drugs, e.g., gemcitabine, are likely to be taken into the cancer cells. This clinical trial will be testing whether 18F-Clofarabine (CFA) could be an imaging agent to measure this aspect of cancer metabolism.