Free PSA as a Predictor of Prostate Cancer

Clinically diagnosed Prostate cancer is suspected due to raised PSA and abnormal DRE. DRE detected prostate cancer is often advanced and not amenable to curative treatment. The use of PSA as a serum marker has revolutionized PCa diagnosis. PSA is specific to the gland but not specific to cancer, therefore, it may be elevated in benign prostatic hypertrophy (BPH), prostatitis and other nonmalignant conditions. There is no universally acceptable PSA cut off, as PCa can be diagnosed in about 7% cases, although less than 1% are clinically significant with PSA of 0-0.5ng/mL ranges. Various modifications of PSA are therefore described including PSA density, PSA kinetics (velocity and doubling time), free/total (f/t) ratio, PHI test, PCA3 etc. f/t PSA is particularly useful in differentiating BPH from PCa for 4-10ng/mL PSA range. It is, however of no use if total PSA is greater than 10ng/mL or in the follow up of patients. There is limited work to indicate its utility in the <4ng/mL group. There are many limitations to the use of f/t PSA as the values can be affected by various preanalytic and clinical factors.