Background of PSAPSA – Prostate-Specific Antigen – was identified in semen in 1966. In 1979, scientists identified PSA in blood – and in 1987 blood levels were first used to screen for prostate cancer. 4
PSA is a protein produced by normal and malignant cells of the prostate gland. When conducting a PSA test, which measures the PSA level in male blood, a blood sample is sent to a laboratory for analysis. The results are typically reported as nanograms of PSA per milliliter (ng/mL) of blood.5
Two prostate cancersThe American Urological Association recommends active surveillance be offered to men who are found to have organ-confined, “low-grade” tumors. This involves shared decision-making between patient and physician. Doctors and scientists have found that those who have low-grade cancer – a slow-growing prostate cancer that doesn’t dramatically worsen – may be better off with just “active surveillance.” Slow-growing, non-aggressive prostate cancer means the patient has a small chance of dying from the disease.6
“Advanced" prostate cancer occurs when prostate cancer spreads outside the prostate, but only to tissue near the prostate (like seminal vesicles). Prostate cancer that has not spread far can be called "locally advanced prostate cancer."7
PSA and free PSAMen above the age of 50 are screened for prostate cancer with a digital rectal exam (DRE) and a PSA blood test. If that number is elevated, it means that the patient could have prostate cancer. But PSA levels can be elevated for a multitude of reasons – two examples being prostatitis (inflammation of the prostate) or benign prostatic hyperplasia (BPH) (enlargement of the prostate).
The only way to truly identify prostate cancer is by performing a prostate biopsy, which comes with some risks: bleeding at the site, blood in semen and/or urine, difficulty urinating and infection.8 PSA testing presents one key problem: Studies have shown that about 75% of men with an elevated PSA (total serum PSA in the range of 4-10 ng/mL) do not have prostate cancer.9 The reasoning lies with specificity: PSA is simply not specific enough when it comes to cancer. Free PSA, as the name states is “free.” While normal PSA is bound to other proteins, free PSA travels alone.
What is p2PSA?PSA is first formed as a precursor, proPSA. p2PSA is a truncated form of proPSA with two amino acids remaining. Valuably, p2PSA is uniquely expressed in cancer cells.
If p2PSA is so great; why do we need phi?phi(Prostate Health Index) is a mathematical formula of three biomarkers ([p2PSA/fPSA] × √tPSA).
phihas a high diagnostic accuracy rate and a better predictive value in patients harboring this aggressive disease.10 The phitest was approved by the Food and Drug Administration (FDA) in 2012 for prostate cancer detection in those with serum tPSA values between 4 and 10 ng/mL.
Low phiscores are associated with a lower probability of finding prostate cancer on biopsy, and higher phiscores are associated with an increased probability of finding prostate cancer on biopsy.11
While PSA is a widely used screening tool for prostate cancer, its limited specificity for cancer necessitates a more precise tool for prostate cancer detection. phiis intended to fill the diagnostic “gap” between PSA screening and a prostate biopsy. Combined with family and patient history, phican be used to determine the best individualized patient-management decisions for those diagnosed with prostate cancer.12