3' Fluoro 3' deoxythymidine

¹⁸F-3'-Fluoro-3'-deoxythymidine or ¹⁸F-FLT is a tumour-specific PET tracer (radiopharmaceutical) . FLT is suitable for monitoring how tumours respond to cytostatic therapy. FLT accumulates in proliferating cells where it indicates the activity of the enzyme thymidine kinase - cell division can characterised by the activity of that enzyme. FLT is phosphorylated as though it were thymidine, and is subsequently incorporated into DNA. Thymidine is essential for DNA replication. Considering that FLT lacks a 3′-hydroxy group, polymerisation of DNA is impeded following incorporating of FLT. FLT indicates changes in tumour cell proliferation by tracking the restoration of nucleosides from degenerated DNA.