[Prostate-specific antigen as a tumor marker of prostate carcinoma]

Prostate specific antigen (PSA) is currently the tumour marker of choice for prostatic carcinoma. Various indices of PSA have been developed in an attempt to refine its sensitivity and improve its clinical value. These include the ratio of serum PSA level and prostate volume, the rate of change of the PSA level with time, age-referenced PSA, and the proportion of free PSA in serum relative to total PSA (free to total PSA ratio). The free to total PSA ratio is lower in patients with prostate cancer than in those with elevated PSA levels due to benign prostatic hyperplasia.