Introducing PCA3

A genetic probe urine test used in the diagnosis of prostate cancer

PCA3 is a urine-based assay used to provide clinicians with information for patients who have an elevated serum PSA, in conjunction with a previous negative prostate biopsy.

Prostate cancer is now the most common cancer in males in the UK, with nearly 20,000 men being diagnosed with the disease.

Prostate Specific Antigen (PSA) is currently the most important biochemical marker for the diagnosis of prostate cancer; but because of its limited specificity, clinically irrelevant tumours and benign abnormalities are also detected. In addition, PSA is used as an indicator of progression or clinical response after treatment for prostate cancer, but the prognostic value of this marker is limited. The limitation of PSA is that it is produced by both malignant and non-malignant tissue and elevated levels are often not confirmed by biopsy.

Biopsy is considered the “gold standard” for the detection of prostate cancer but the introduction of PCA3 may contribute to a decision on whether or not to proceed to prostate biopsy. The assay measures the expression of mRNA from the PCA3 gene.

PCA3 is specific to the prostate, over expressed only by malignant tissue, and is significantly upregulated (60-100 fold) in prostate cancer. PCA3 mRNA, along with the mRNA of PSA is measured quantitatively and examined as a ratio. High ratios have been shown to be indicative of prostate cancer. PCA3 may provide assistance in follow-up treatment in patients with an elevated serum PSA and negative biopsy results.

PCA3 utilises whole urine collected following a digital rectal examination (DRE). The DRE releases prostate cells through the prostate duct system into the urinary tract, where they can be collected in the first catch urine. Gen-Probe urine sample collection kits must be used.

Higher PCA3 Scores correlate with higher probability of a positive prostate biopsy.

By measuring the expression of mRNA from the PCA3 gene, this new assay provides greater accuracy: a positive result may indicate prostate cancer and the need for an additional biopsy; a negative result accompanied by a PSA greater than 4 ng/ml suggests that a relatively longer time interval may be acceptable between biopsies.

Further information concerning this test can be obtained by contacting Mr Thilagarajah’s secretary.