Using a PET Imaging Agent, 18F-Clofarabine (CFA), to Measure Deoxycytidine Kinase Activity in Metastatic Cancer

The participants enrolled will receive a baseline CFA PET/CT evaluation. Then, the participants will undergo the routine follow up would normally occur for their cancer and its treatment. If this routine follow up and care involves repeat imaging of the cancer, then the CFA PET/CT scan will be repeated at that time (timed according to standard-of-care follow-up imaging), which is expected between a month to about 4 months after the first CFA PET/CT scan. The study period will end 24 hours after this repeat PET/CT scan.