FREE TOTAL PROSTATE-SPECIFIC ANTIGEN RATIO - HOPE AND CONTROVERSIES/

Prostate-specific antigen (PSA) forms in serum two stable complexes wi th alpha(1)-antichymotrypsin and alpha(2)-macroglobulin. PSA complexed to alpha(1)-antichymotrypsin is the predominant fraction of PSA. A mi nor fraction of serum PSA is not associated with proteinase inhibitors . These molecular differences explain the possibility to distinguish f ree from total PSA (F/T ratio), Free and complexed PSA have different clearances and significant differences between clearance of free PSA a fter radical prostatectomy (RP) and after open surgery for benign pros tatic hyperplasia (BPH) are observed, These differences are explained by the entire removal of prostatic cells responsible for PSA synthesis and storage during RP, i.e. the source of free PSA present in the int ravascular pool. The proportion of free PSA is significantly lower in patients with prostate cancer than in patients with BPH. Thus, the mea n F/T ratio in prostate cancer is lower than that in BPH and may be he lpful to distinguish cancer from BPH especially in the gray zone of to tal PSA (4-10 ng/ml). The reason why complexed PSA increases in patien ts with prostate cancer remains unknown but could be explained by the requirement of an enzymatically active PSA released by the malignant p rostate tissue to bind to alpha(1)-antichymotrypsin. However, a consen sual threshold value for L/T ratio is vet to be found to be of widespr ead clinical use in the differential diagnosis between cancer and BPH.