PCA3 (prostate cancer antigen 3)
Besides the above-described long-established prostate screening methods, the past 14 years have seen research into other diagnostic markers to increase the efficiency of prostate cancer detection, thereby being able to perform needle biopsies more selectively. In 1999, it was reported for the first time that the “prostate cancer antigen 3” is only expressed in prostate cancer cells, but not in benign prostate cells or other tissue. A few years later, a method was developed to detect PCA3 in the urine, which was correlated with a high specificity (between 80% and 90%, depending on the cut-off) for the presence of prostate cancer.
In contrast to PSA, the PCA3 directly correlates with the tumour volume and the histological subtype. The PCA3 test is regarded as an additional tool for detecting a tumour predominantly in patients with elevated PSA levels and negative needle biopsy, making it easier for the urologist to decide whether to perform a repeat biopsy or follow-up. A high PCA3 level is associated with a significantly higher probability of detecting a tumour as part of a repeat biopsy.
PSA is better suitable as a screening method than PCA3, but the latter has a significantly higher specificity (90%) and can be used predominantly in patients with still elevated PSA levels after a first negative needle biopsy to decide whether or not a repeat needle biopsy should be performed directly.
Despite these promising results, the PCA3 test cannot replace the measurement of serum PSA levels and should only be used in individual cases.