Prostate-Specific Antigen As A Diagnostic Tool: How Useful and Reliable Is It?

Abstract

Prostate-specific antigen (PSA), a kallikrein isolated by Wang in 1979 [1], is a physiologic excretory product of the healthy prostatic epithelium, involved in the semen liquefaction process. A small amount of PSA (less than 1 molecule per million excreted) leaks into the bloodstream where its normal level was – arbritarily – fixed more than 2 decades ago at 4 ng/ml and shown to rise in any prostatic pathologic condition associated with alterations of the basement membrane: prostatitis, benign prostatic hypertrophy (BPH) and, of course, cancer. While definitely not a tumor marker, PSA has been used and approved as a marker for the detection of prostate cancer [1] and therefore, extensively promoted as the marker for early detection and eventually, screening. This has induced an unprecedented revolution in urology and oncology, leading to a spectacular increase in the incidence of prostate cancer, inducing a dramatic expansion of surgery and radiation therapy without any spectacular modification of the prostate cancer death rate up to this point in time. However, once initially seen as a ‘magic bullet’, PSA is increasingly confronting clinicians with more questions than they seem able to answer, which this editorial will try to summarize.