Prostate cancer (CaP) is one of the most frequently occurring malignancies in Western countries (1), and its relevance is expected to increase in the near future because it tends to increase with age more rapidly than many other cancers. Early diagnosis is of paramount importance because the disease is curable only when confined to the gland. Several studies have shown that Caps detected by screening are frequently organ-confined (2-4), although a major impact of CaP screening on patient survival has not yet been demonstrated. The serine protease prostate-specific antigen (PSA) was shown to be a useful prostate-specific tumor marker soon after it was first detected (5). However, several studies have shown that serum PSA concentrations between 4 and 10 [micro]g/L were not accurate for CaP diagnosis (6, 7).