Predictive Value of Prostate-specific Antigen Isoform p2psa and Its Derivates in the Diagnosis of Prostate Cancer

In Europe, prostate cancer (PCa) is the most common solid neoplasm, with an incidence rate of 214 cases per 1000 men, outnumbering lung and colorectal cancer. Early detection tests have been developed in order to identify PCa while it is still confined to the prostate gland. The two most commonly used tests are digital rectal examination and serum prostate-specific antigen (PSA) level: however, most of cases is detected in the so called T1c stage, i.e. for PSA increasing only. As marker, PSA is organ-specific but not cancer-specific, and its levels may change as result of physical activity, sexual activity, in the presence of benign prostatic hyperplasia (BPH), acute and chronic prostatitis, as well as in the presence of PCa. A total serum PSA of 4.0 ng/ml has traditionally been used as threshold for considering prostate biopsy and large programs for the early detection of prostate cancer have shown that almost 70% of cancer cases can be detected using a PSA cutoff of 4.0 ng/ml. However, using a PSA threshold of 4.0 ng/ml 20% to 25% of prostate cancer cases are not detected (false-negative) and the false-positive rate is 65%. To improve the usefulness of PSA for identifying patients who require biopsy, the PSA threshold has been lowered at 2 ng/ml; moreover, the levels of free and bound PSA have been assessed, together with PSA density (the rate of PSA over the prostate volume) and PSA velocity (the rate of PSA increase), which seem to have some validity for detecting prostate cancer. Recent studies have shown that other new biomarkers could be used in the diagnosis of early prostate cancer as they showed a higher sensitivity and specificity. In the last two years, several investigators showed that PSA isoform \[-2\] proPSA (p2PSA) and its derivatives, namely, percentage of p2PSA to free PSA (%p2PSA) and the Prostate Health Index \[PHI; (p2PSA / free PSA) × √tPSA)\] improve the accuracy of total PSA (tPSA) and percentage of free PSA (%fPSA) in predicting the pres