This clinical trial studies 18F-clofarabine positron emission tomography (PET)/computed
tomography (CT) in imaging patients with cancer before and after treatment with a therapy
that activates the patient's immune system (immunotherapy). PET/CT scans give detailed
pictures of areas inside the body. 18F-clofarabine is a drug that contains a radioactive
substance that is taken up by cells expressing deoxycytidine kinase (dCK), which is highly
expressed in activated immune cells, making them light up during PET/CT scans. Doctors also
want to know how 18F-clofarabine is distributed throughout the body before and after
treatment with immunotherapies.