PCA3

The PCA3 test is used to help decide whether a repeat prostate biopsy should be performed on a man age 50 or older who has had one or more previous negative biopsies.

The test may be ordered when a man has had an elevated PSA blood test and/or abnormal digital rectal exam (DRE) and one or more previous negative prostate biopsies. It may be ordered when another biopsy would normally be recommended and a health practitioner wants to evaluate the likelihood that the repeat biopsy would be positive.

The PCA3 test result is a ratio of PCA3 mRNA to PSA mRNA that is reported as a score. The laboratory report provides a cut-off number at which the score is considered positive.

The PCA3 test does not provide a definitive answer as to whether a man has a cancer or not. Rather, healthcare practitioners consider the test results in conjunction with other laboratory and clinical data to determine the likelihood that a repeat biopsy will be positive.

A PCA3 score that is less than the laboratory’s established cutoff is considered negative and is associated with a decreased likelihood of a positive biopsy.

A PCA3 score that is greater than the laboratory’s established cutoff is considered positive and is associated with an increased likelihood of a positive biopsy. Some labs provide a range in which PCA3 is considered positive but with a caution about interpreting results that are close to the cut-off value, due to normal test variability.

About 90% of prostate cancers will over-express PCA3, but the PCA3 result cannot be used to diagnose or completely rule out prostate cancer. It just helps to guide decision-making on performing another biopsy. Prostate biopsy is still the gold standard for diagnosing prostate cancer.

Many prostate cancers are slow-growing and not considered clinically significant. A man who has prostate cancer is more likely to live with the condition and die of something else. Prostate cancer may be managed through “watchful waiting” and treated if or when needed. Some prostate cancers, however, are aggressive and can grow and spread throughout the body. Distinguishing between the two can be challenging but is important. In recent years, there has been considerable concern about over-diagnosing and over-treating prostate cancers that are not clinically significant. In part, this is because the treatments carry the potential for significant complications that can impact a man’s quality of life, including urinary incontinence and erectile dysfunction.

The medical community has become increasingly conservative about recommending PSA as a screening tool in asymptomatic men and are eager to find additional tools that can aid in decision-making. PCA3 is one of these tools.

A wide range of other tests and biomarkers are being investigated.

No, the DRE is a very necessary part of the sample collection. The procedure releases prostate cells and PCA3 into the urine, where it can be detected. This is why it is also important to collect the first amount of urine after the DRE – so the released PCA3 is present in the urine sample.

The DRE will be performed in your healthcare practitioner’s office and, most likely, so will the urine collection as it is the first urine collected after the DRE. However, the testing requires specialized equipment and your sample will be sent to a laboratory for testing. Not all labs perform this test, so your sample may be sent to a reference laboratory.

No, it is not over-expressed in every cancer, so about 10% of prostate cancers will have normal PCA3 results.