• The main diagnostic biomarker in current use is prostate-specific antigen (PSA) and it is one of the recommended diagnostic tools from the European Association of Urology Guidelines on prostate cancer. • One of the challenges with PSA is that men with very low levels of PSA can harbour prostate cancer, making it difficult to set a lower limit. • Several modifications to PSA biomarker detection have been suggested to improve its sensitivity and selectivity including PSA density, free:total PSA, PSA velocity/doubling time and different PSA isoforms. • However, there remains a need to improve accuracy of diagnosis and this has led to research in to a number of promising new biomarkers. • These include genetic and blood or urine based biomarkers. The most advanced of these is prostate cancer gene 3 found in urine and developed into a commercial test in 2006. • Other promising markers include circulating tumour cells (CTC) in blood, which have been correlated with survival in castration-resistant prostate cancer. A system for evaluating CTC was approved by the USA Food and Drug Administration in 2008.
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