PCA3 is a prostate specific gene that is highly over-expressed in prostate cancers. The PCA3 assay is an in vitro nucleic acid amplification test that measures the concentration of prostate cancer gene 3 (PCA3) and prostate-specific antigen (PSA) RNA molecules in post-digital rectal exam (DRE) male urine specimens. The assay calculates the ratio of PCA3 RNA molecules to PSA RNA molecules to generate a PCA3 score. Studies have shown that because the PCA3 gene is highly specific for prostate cancer, the PCA3 score predicts the results of repeat biopsies more accurately than traditional serum PSA testing in men who have had one or more previous negative prostate biopsies.

PCA3 is purported to be a more specific test to guide the decisions about performance of prostate biopsy than PSA. Several studies were followed by and prospective, multi-centre US study in 466 men recommended for a repeat biopsy confirms the utility of the PCA3 (Prostate CAncer gene 3) Assay for predicting repeat biopsy outcome. It was concluded that the PCA3 Assay supplements serum PSA and other clinical information for more accurate prediction of repeat biopsy outcome. Men with PCA3 Scores < 25 were 4.56 times more likely to have a negative repeat biopsy as men with PCA3 Scores ≥ 25. The PCA3 Assay provides clinicians and patients with independent, clinically useful information to make more informed repeat biopsy decisions. However, how to use this assay clinically is still unknown and more studies would be needed to clarifyit.h

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Marks LS, et al. PCA3 molecular urine assay for prostate cancer in men undergoing repeat biopsy.Urology 2007;69:532-5

Aubin SM, et al. PCA3 molecular urine test for predicting repeat prostate biopsy outcome in populations at risk: validation in the placebo arm of the dutasteride REDUCE trial.J Urol 2010;184:1947-52