Background: \- The drugs FdCyd (also called 5-fluoro-2'-deoxycytidine) and THU (also called tetrahydrouridine) are being used in a cancer treatment study. Not a lot is known about how FdCyd works in the body. Researchers want to look at a modified form of FdCyd using imaging studies to see how the drug reacts with the cancer. This study is not a treatment study. It is open only to people who are already on the FdCyd and THU cancer treatment study. Objectives: \- To study how FdCyd affects advanced cancer cells. Eligibility: \- Participants in National Cancer Institute study 09-C-0214. Design: * Participants will have two imaging studies, one before starting FdCyd and THU treatment and one after starting treatment. * Participants will have the modified FdCyd, known as F-18 FdCyd, with a dose of THU. The doses will be followed by two imaging study scans and frequent blood samples. * This procedure will be repeated at a later date, during the FdCyd and THU treatment period. * Treatment will not be provided as part of this study. This is an imaging study protocol only....
* INCLUSION CRITERIA: * Enrolled in the National Institutes of Health (NIH) Phase II Clinical protocol evaluating 5-fluro-2'-deoxycytidine (FdCyd) with Tetrahydrouridine (THU) (09-C-0214) with target lesion measured as greater than or equal to 10mm with spiral computed tomography (CT) scan. * Written, voluntary, informed consent of the patient must be obtained in compliance with institutional, state and federal guidelines * For females: Negative serum pregnancy test OR post-menopausal for at least 2 years OR patient has had a hysterectomy EXCLUSION CRITERIA: * Participants with severe claustrophobia unresponsive to oral anxiolytics * Subjects weighing \> 400 lbs (weight limit for scanner table), or unable to fit within the imaging gantry * Known allergy to FdCyd * The subject is unable to lie still for 75 minutes * 5 Pregnant or lactating women. Pregnant women are excluded from this study because the effects of 18F-FdCyd in pregnancy are not known. Because there is an unknown but potential risk for adverse events in nursing infants secondary to administration of 18F-FdCyd in the mother, breastfeeding should be discontinued if the mother receives 18F-FdCyd * Participants with any co-existing medical or psychiatric condition that is likely to interfere with study procedures and/or results