Using Genetic Biomarkers in Prostate Cancer Diagnoses- A Review.

 

Looking for something? Sandhill cranes in my yard.  Photo: BJ Gabrielsen

Looking for something? Sandhill cranes in my yard. Photo: BJ Gabrielsen

New research has identified several ‘biomarkers’ or genetic fingerprints that report the underlying biology of a tumor. Combinations of these biomarkers can aid clinical management of prostate cancer by:  1) allowing accurate diagnoses;  2) establishing whether a patient’s cancer is aggressive or indolent;  3) deciding if repeat biopsies are needed;  4) aiding clinical decisions on therapeutic options (drug combinations for maximal patient benefit);  and,  5) evaluating whether a patient’s cancer is responding to therapy or not. For an excellent review article describing many of the diagnostic (including genetic) tests currently available or in the developmental pipeline, see the March 29th, 2013 Prostate Cancer Foundation (PCF) NewsPulse  and the articles contained therein.  Many of these biomarker-driven diagnostic / prognostic tests nearing clinical use are in the final stages of clinical validation and are listed in table form in the Newspulse article. The New York Times recently published a feature article  discussing many of these new tests. These latest prostate cancer tests evaluate blood, urine or prostate biopsy specimens for the presence of either an abnormal gene activity pattern, or specific chemicals that are released by cancer cells. For example, the GenProbe test currently evaluates urine samples for the expression of PCA3 (prostate cancer antigen) DNA. It is anticipated that the GenProbe test evaluating both PCA3 DNA and expression of the TMPRSS2-ERG gene fusion will soon be approved for use. The abnormal TMPRSS2-ERG gene fusion is present in 50 percent of all prostate tumors, and PCA3 is expressed at high levels in 95 percent of prostate cancer patients, therefore the combination of these two tests has a high probability of accurate diagnoses. Testing these biomarkers in urine samples holds potential due to the non-invasiveness of urinalysis, ease of collection, and the fact that prostate cells are directly released into the urethra through prostatic ducts after a digital rectal exam (DRE) or prostate massage.

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