The PCA3 GeneTest
PROGENSA PCA3, the world's first gene-based urine test developed in the United States, is a molecular genetic screening of the urine. PCA3 (Prostate Cancer gene 3) is a gene that is expressed exclusively in the prostate tissue and is passed in the urine. In case of metastases, the gene is especially active, and the prostate carcinoma cells form 60 – 100 times more PCA3 than normal prostate tissue.
While the laboratory procedure is technically very involved, the actual test is comparably simple: after a massage is given to the prostate through palpation, the patient will urinate. The previously administered massage causes the prostate cells to be discharged with the urine. The urine sample will then be sent to a specialized laboratory to determine the PCA3 score. In the laboratory, a so-called transcription mediated amplification (TMA) will be performed, and within 15 to 30 minutes, the RNA in the urine sample will be quantified a billion-fold. Two enzymes specifically fitted to the PCA3 messenger RNA, will then yield the grade of concentration in the PCA3 level.
Above a score of 35, according to the producer GenProbe, there should be about a 50% chance that with a biopsy tumor tissue will be found. Above a score of 100, the hit rate is allegedly about 70%.
Current studies showed that with elevated PCA3 scores, a prostate biopsy more often is positive, meaning that cancer cells in the prostate are present. However, a low PCA3 score points to a lower possibility of a positive biopsy. This means that the urine test differentiates more accurately between prostate cancer and benign prostate diseases, such as a benign prostate enlargement or prostatitis (inflammation of the prostate).
Suitable candidates for the new urine test are in particular patients, with a persistently elevated PSA after a negative biopsy, and who are still suspected of having prostate cancer based on an elevated PSA.
However, a negative test result cannot completely rule out the presence of a tumor in the prostate. The PCA3 test does consequently not a replace a biopsy, but is rather an additional screening method in the diagnostic spectrum.
Also for patients with a large prostate, it can be meaningful to take the PCA3 test, since often the PSA scores are elevated without the presence of a carcinoma. Obviously the more aggressive the cancer, the higher the PCA3 score. In the future, this could be helpful in deciding whether a prostate tumor must be treated or may just remain under observation.
The cost for a PCA3 screening is between 300 and 350 Euro, and currently the test is only paid for by private health insurances.
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