LabCorp and its Specialty Testing Group, a fully integrated portfolio of specialty and esoteric testing laboratories.
To help determine if a repeat prostate biopsy is indicated to help detect prostate cancer
When a healthcare practitioner is considering a repeat prostate biopsy for a man age 50 or older who has had one or more previous negative biopsies
The first amount of urine collected after a healthcare practitioner performs a digital rectal exam (DRE)
The prostate cancer antigen 3 (PCA3) test detects genetic material (messenger RNA (mRNA)) that is produced only by the prostate. The protein PCA3 and its associated mRNA are present at low levels in normal prostate tissue. PCA3 is present in increased amounts (over-expressed) in about 90% of prostate cancers. Prostate specific antigen (PSA) is also produced in increased amounts by prostate cancers but can be increased in a number of benign conditions as well.
This test measures PCA3 mRNA and PSA mRNA in the first urine sample collected following a digital rectal exam (DRE). Laboratories report a score based on the ratio of PCA3 mRNA to PSA mRNA called the PCA3 score.
Prostate cancer is the uncontrolled growth of cells in the prostate, a small gland that encircles the urethra in men. Some men may choose to undergo screening for prostate cancer using a PSA blood test. An increased PSA level is associated with an increased risk of prostate cancer, but PSA can also be increased with benign prostatic hyperplasia (BPH), prostatitis, infection, and a variety of other temporary conditions.
Diagnosis of prostate cancer requires performing a prostate biopsy and identifying cancer cells under the microscope. This biopsy may be done after an increased PSA result and/or an abnormal DRE. The accuracy of biopsies depends on the number of tissue samples and the sites from which they are taken. Since the biopsy takes small tissue samples, and since PSA is not cancer-specific, the initial biopsy is often negative.
A negative initial biopsy may leave the healthcare practitioner questioning whether the patient is truly cancer-free or if the cancer has been missed. Concerns over missing clinically significant cancer may prompt additional biopsies, especially if a repeat PSA is still elevated or has increased. However, each biopsy has potential complications, such as discomfort, blood in the urine (hematuria) or semen, rectal bleeding, difficulty urinating, infection, and in rare cases septicemia, so minimizing the number of biopsies performed is also desirable.
The PCA3 test can help determine if a repeat prostate biopsy would likely be positive and whether a man may avoid an unnecessary repeat biopsy. PCA3 is significantly over-expressed with prostate cancer but (unlike PSA) it is not affected by prostatitis or BPH.
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 healthcare 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 (See Screening Tests for Adults (30-49): Prostate cancer and Screening Tests for Adults (50 and Up): Prostate cancer for details on screening recommendations) 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.
(2018 April 5). Prostate Cancer Early Detection. NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines ®) Version 2.2018. Available online at https://www.nccn.org/professionals/physician_gls/pdf/prostate_detection.pdf Accessed on 04/07/18.
Strong, A. and Deane, L. (2017). Contemporary Role of Biomarkers In the Evaluation, Stratification, And Treatment Determination in Men at Risk for and/or Diagnosed With Prostate Cancer. Urol Nurs. 2017;37(4):192-203. Urologic Nursing. Available online at https://www.medscape.com/viewarticle/892905. Accessed on 04/07/18.
Ashley, V.A. et. al. (2017). The Use of Biomarkers in Prostate Cancer Screening and Treatment. Rev Urol. 2017;19(4):221-234. Available online at https://www.ncbi.nlm.nih.gov/pubmed/29472826. Accessed on 04/07/18.
NCI Staff. (2017 June 9). Biomarker Test Could Reduce Unnecessary Biopsies to Detect Prostate Cancer. National Cancer Institute. Available online at https://www.cancer.gov/news-events/cancer-currents-blog/2017/biomarkers-urine-prostate-biopsy. Accessed on 04/07/18.
Genzen, J. et. al. (2018 April, Updated). Prostate Cancer – PSA. ARUP Consult. Available online at https://arupconsult.com/content/prostate-cancer. Accessed on 04/07/18.
(2015). Early Detection of Prostate Cancer. American Urological Association. Available online at https://www.auanet.org/guidelines/early-detection-of-prostate-cancer-(2013-reviewed-and-validity-confirmed-2015). Accessed on 04/07/18.
Deng, J. et. al. (2017 March 7). Long Non-Coding RNA as Potential Biomarker for Prostate Cancer: Is It Making a Difference? Int J Environ Res Public Health. 2017 Mar; 14(3): 270. Available online at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5369106/. Accessed on 04/07/18.
(© 1995–2018). PCA3 (Prostate Cancer Antigen 3). Mayo Clinic Mayo Medical Laboratories. Available online at https://www.mayomedicallaboratories.com/test-catalog/Overview/75211. Accessed on 04/07/18.
(2018 January 4, Updated). Key Statistics for Prostate Cancer. American Cancer Society. Available online at https://www.cancer.org/cancer/prostate-cancer/about/key-statistics.html. Accessed on 04/07/18.
(2018 February 22, Updated). Prostate Cancer Screening (PDQ®)-Patient Version. National Cancer Institute. Available online at https://www.cancer.gov/types/prostate/patient/prostate-screening-pdq#section/_13. Accessed on 04/07/18.
Cheuck, L. et. al. (2017 September 21, Updated). Prostate Cancer Diagnosis and Staging. Medscape Urology. Available online at https://emedicine.medscape.com/article/458011-overview. Accessed on 04/07/18.
Chunhua, L. et. al. (2018 March 21). Clinical Significance of Peripheral Blood PCA3 Gene Expression in Early Diagnosis of Prostate Cancer. Transl Oncol. 2018 Mar 21;11(3):628-632. Available online at https://www.ncbi.nlm.nih.gov/pubmed/29574327. Accessed on 04/07/18.
Davenport, L. (2015 January 12). Questions Remain Over Role of PCA3 Assay in Prostate Cancer. Medscape Oncology News. Available online at https://www.medscape.com/viewarticle/837934. Accessed on 04/07/18.
Reuters Staff. (2017 May 25). Urinary RNA Testing Helps Identify Aggressive Prostate Cancer. Medscape News. Available online at https://www.medscape.com/viewarticle/880543. Accessed on 04/07/18.
Feng, F. et. al. (2014). Current and Future Applications Of Genetic Prostate Cancer Screening in the Urologic Clinic. Urol Nurs. 2014;34(6):281-291. Available online at https://www.medscape.com/viewarticle/840844. Accessed on 04/07/18.