Advances in the application of prostate-specific antigen in the detection of early-stage prostate cancer.

Prostate-specific antigen (PSA) has revolutionized the detection of prostate cancer. PSA-based screening has been shown to be effective in detecting prostate cancer at an early, potentially curable stage; however, this tumor marker is limited by appreciable false-positive and false-negative results. This is especially problematic when the PSA level is in the upper limit of normal (2.5 to 4.0 ng/mL) or the intermediately increased range (4.1 to 10.0 ng/mL). Several PSA-related indexes and assays have been proposed in an attempt to improve the power of PSA in the early detection of prostate cancer: PSA density (PSAD), age-referenced PSA, volume-referenced PSA, PSAD of the transition zone (PSA-TZ), ProstAsure Index, (Global Health Net, Savannah, GA) and percent free PSA. These indexes may improve the sensitivity and specificity of PSA-based screening, facilitating the early detection of prostate cancer and reducing the number of unnecessary biopsies.