Wednesday, 21 February 2018

Ratio of free to total PSA (prostate-specific antigen)

«The end product of normal PSA (prostate-specific antigen) biosynthesis within the prostate epithelium and ducts is inactive "free PSA", a fraction of which diffuses into circulation. In prostate cancer, tumors disrupt the prostate basement membrane and allow precursor forms of PSA to leak into the circulation, which decreases the relative proportion of free PSA. Hence, the ratio of free-to-total PSA will be lower in men with prostate cancer. A ratio of <7% is highly suspicious for prostate cancer, whereas a ratio of >25% is rarely associated with malignancy.»
Bibliographic reference: Shah A. 53 - Low-Risk Prostate Cancer. In: Hristov B, Lin S, Christodouleas J. Radiation Oncology. 2nd ed. Philadelphia, USA: Wolters Klumer Health; 2015:366.