PCA3 Urine Test for Prostate Cancer

 

The PCA3 Test Provides an Answer

The PCA3 test for the detection of prostate cancer is highly specific and more precise than all other available screening tests for prostate cancer. The PCA3 test is a molecular biology assay that measures the expression of PCA3 (prostate cancer gene 3) mRNA in urine samples. PCA3 is specific to the prostate and is significantly up-regulated in prostatic cancerous cells. The test quantitatively measures PCA3 mRNA as well as PSA mRNA and determines their ratio. High ratios have been shown to be indicative of prostate cancer.

PCA3 screening may help reduce the number of unnecessary biopsies. In addition, the test is non-invasive, eliminating pain and discomfort associated with biopsies. Dynacare Next is the first laboratory to offer this service in Canada.

The PSA Dilemma

There are two tests that are commonly used to help detect prostate cancer early: the digital rectal exam (DRE) and the prostate-specific antigen (PSA) test. However, these methods pose a significant dilemma. Sometimes men with prostate cancer have PSA levels that are not higher than normal. Conversely, a significant portion of men with abnormal PSA levels will have negative biopsies. Therefore, there is a critical need to address the diagnostic challenge of detecting prostate cancer in men with abnormal PSA concentrations.

Until now, no acceptable marker has been available to help physicians determine repeat biopsy intervals on patients with abnormal PSA levels and a negative biopsy. The PCA3 test offers a potential solution to this clinical diagnostic challenge, by providing a result that could help physicians select patients for a repeat biopsy.

How the PCA3 Test Works

The PCA3 Test measures both PCA3 and PSA mRNA in a urine sample collected following a DRE. The PSA mRNA measurement ensures that prostate cells were collected in the sample and also provides a means to normalize the PCA3 mRNA amount. The result is reported as a ratio of PCA3 mRNA to PSA mRNA, which translates to a low or high risk of having prostate cancer.

Using transcription-mediated amplification technology, PCA3 and PSA mRNA molecules are amplified from the sample. Given that PCA3 can be 60-fold overexpressed in a cancer cell versus a normal cell1, samples containing cancer may have higher PCA3/PSA ratios than those that do not.

The measured PCA3/PSA ratios allow us to establish the risk of having prostate cancer. The risk is expressed either as low or high. PSA mRNA measurements below a certain detection amount will produce an inconclusive test, indicating that insufficient prostate cells were detected.

1Hessles, et al. (2003) European Urology, 44:1.