INTERPRETATION OF FREE PROSTATE-SPECIFIC ANTIGEN CLINICAL RESEARCH STUDIES FOR THE DETECTION OF PROSTATE-CANCER

Purpose: We reviewed the use of percent free prostate specific antigen (PSA) to enhance specificity of PSA testing and aid in the discrimina tion of benign and malignant prostate disease. We present proposed per cent free PSA cut points and probability factors, and discuss factors that are believed to affect study outcomes and conclusions. Materials and Methods: We reviewed the Literature with respect to PSA and free P SA with particular emphasis on clinical use of percent free PSA and fa ctors that may affect study outcomes. Results: Percent free PSA may in crease the specificity of PSA testing without sacrificing the cancer d etection rate. Differences in study designs and subject populations ma y account for the confusion in the current literature. Specific factor s that may influence study outcomes include sample size, PSA range, ag e, race, digital rectal examination findings, prostate size, tumor siz e and pathology, as well as treatment history, sample collection and s torage conditions, and the particular assays used to determine free an d total PSA values. Conclusions: The use of percent free PSA to enhanc e the specificity of prostate cancer screening is thought to provide u seful information to aid in the differentiation of benign and malignan t prostate diseases. There is evidence to suggest a benefit cost advan tage to a tailored biopsy approach based on percent free PSA. However, statistically valid multisite clinical trials that take into account influencing factors are needed to set assay specific cut points and pr obability determinations.