New and more accurate tests are needed to screen for and diagnose prostate cancer (PCa); the PCA3 gene test may be a part of the answer. Prostate cancer is one of the most common cancers in men with more than a million new cases diagnosed each year. Characterized by an overgrowth of cells in the prostate, PCa has no single accurate diagnostic test and is often over-diagnosed. Science and medicine have been collaborating on new ways to improve the early identification of prostate cancer by identifying new screening markers.1
For years doctors have been using the Prostate-Specific Antigen (PSA) Test and digital rectal exam (DRE) to screen and detect prostate cancer.1 Yet the results of these tests have limitations due to their false positive rates, which may result in unneeded biopsies and overtreatment of clinically insignificant cancers.2Decisions to biopsy should be made based on a good medical history and the most accurate clinical testing available.1
PCA3 is a genetics based tool
The prostate cancer antigen 3 gene (PCA3) test is used to help determine your risk of PCa by identifying a genetic marker and elevated PSA levels. The PCA3 gene is present in all prostate gland cells.1 When the PCA3 gene overexpresses, cancerous prostate cells make more of the protein that leaks into the urine. Therefore higher PCA3 levels are more likely to be caused by prostate cancer than by another prostate condition. It is not used as a stand-alone test to diagnose prostate cancer.
How does PCA3 work?
There is no specific preparation for a PCA3 test.1 It takes place in the doctor’s office and is a 2-part test consisting of a digital rectal exam and a urine test. First comes the DRE. In addition to the tactile exam, the doctor will massage the prostate 3 times in order to help release more PCA3 proteins into the urine.1,2
The urine portion of the test is called the first catch. It specifically requires the collection of the first 20 to 30 mL of urine after a digital rectal exam.4 The accuracy of results decreases without DRE.2,4
What does it measure?
The PCA3 biomarker is 60 to 100 times greater in cancerous than in benign prostate tissue cells. PCA3 concentration has such specificity it can identify malignant from benign prostate cells with nearly 100% accuracy.2,7
Prostate-specific antigen, a protein made by the prostate, can be an indicator of prostate cancer or other prostate-related medical problems including, but not limited to, an enlarged prostate, inflammation or infection.1,2,3 Routine PSA screening may over indicate prostate cancer at a significant rate, from 17 to 50 percent of the time.1 There is a need for improved diagnostic tools and more accurate information that should result in fewer biopsies being performed.4
A digital rectal exam (DRE) is performed by a doctor who inserts a lubricated and gloved finger into the rectum to feel the prostate gland. They feel for lumps, growths or tumors, or anything else unusual.1 As a stand-alone test, it has poor predictive value because there is no uniform measure, it is based on the skills and reporting variables of each individual physician.2
Inconclusive PSA tests or inconclusive digital rectal exams.
Elevated PSA with negative biopsy
Presence of cancer with low PSA levels
Elevated PSA and prostatitis
Understanding your test results
A low PCA3 score, less than 20, indicates a decreased likelihood of prostate cancer and your doctor may decide to delay or avoid a surgical biopsy. On the other hand, a high PCA3 score, over 60, suggests the need for a biopsy as there is a greater probability of finding cancer. Different studies have utilized variable cutoff scores. The FDA has approved PCA3 to be considered along with other factors. These can include both clinical and lab findings, as a determinant of conducting a repeat biopsy in men over 50 who have had a negative prostate biopsy in the past.2 The factors may include age, race, and family history in addition to the clinical findings.
Talk to your doctor
You may want to check to see if the PCA3 test is covered by your health insurance plan. Many companies will not pay for PCA3 testing, which can run between $200 and $500 dollars.1,6 Your doctor can help you make a cost-effective plan that provides the right testing for you.
Like the 4Kscore test, the PCA3 is another approach to evaluating whether a biopsy of the prostate is necessary.6 As the number of unnecessary biopsies is reduced, medical complications can be decreased, and costs reduced.6 Studies have demonstrated that a high PCA3 score correlates with an elevated risk of finding cancer.2 Doctors can use PCA3 results along with thorough patient information to make better informed decisions on the need for prostate biopsies.
Galan, N. All you need to know about the PCA3 test. Available at: https://www.medicalnewstoday.com/articles/319675.php. Accessed 2.25.19
Progensa PCA3 assay Available at: http://www.pca3.org/. Accessed 2.21.19
What is a PCA3 Test? Available at: https://www.healthline.com/health/prostate-cancer/pca3-test. Accessed 2.22.19.
Marks, L., Bostwick, D. Prostate Cancer Specificity of PCA3 Gene Testing: Examples from Clinical Practice. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2556484/. Accessed 2.25.19.
The Biopsy Decision Clarified. Available at: http://www.morrisurology.com/OPKO-4Kscore-Test-Brochure-Final.pdf. Accessed 2.25.19.
What is the 4K Score Test For Prostate Cancer. Available at: https://4kscore.com/. Accessed 2.23.19.
Marks, L. and Bostwick, D. Prostate Cancer Specificity of PCA3 Gene Testing: Examples from Clinical Practice. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2556484/ Accessed 2.25.19