Nucleoside-based probes for imaging tumor proliferation using positron emission tomography

Cancer is one of the leading causes of human death, and early detection can be beneficial for its timely therapy and management. For the early detection of cancer, positron emission tomography (PET) is more accurate and sensitive than other imaging modalities, such as computed tomography and magnetic resonance imaging. [(18) F]-Labeled fluorodeoxyglucose is the most useful PET probe in early detection of cancer; however, its nonspecific accumulation and consequent false-positive findings warrant the identification of other PET probes. Thymidine (TdR) and its analogs have been radiolabeled for PET imaging of cellular proliferation and DNA synthesis. Because of its in vivo instability, radiolabeled TdR has not been successful in PET imaging. However, some of its radiolabeled analogs have been developed for PET imaging of cellular proliferation and DNA synthesis. In this review, the radiochemistry and production of (11) C-TdR and (11) C/(18) F-labeled TdR analogs published to date are presented.