Serum half-life time determination of free and total prostate-specific antigen following radical prostatectomy--a critical assessment.

OBJECTIVES All studies investigating the elimination kinetics of serum total (tPSA) and free (fPSA) prostate-specific antigen (PSA) were carried out in men undergoing radical prostatectomy. Radical prostatectomy itself could, however, have a major influence on the serum concentration of these tumor markers (e.g., perioperative fluid shift or blood loss). The purpose of our study was to determine the half-life time of fPSA and tPSA with special regard to the influence of the radical prostatectomy on the serum concentration of these tumor markers. METHODS Eleven men (mean age 63.2+/-7.2 years) with organ-confined prostate cancer who underwent radical prostatectomy were investigated (final pathologic Stage pT2pN0 or lower). Serum samples were obtained preoperatively and 0.25, 0.5, 1, 2, 4, 8, 12, 16, 24, 48, 72, 120, 168, and 240 hours after removal of the prostate. fPSA and tPSA and albumin and total protein serum concentrations were determined in all samples. RESULTS During the first 120 minutes after removal of the prostate, albumin and total protein serum concentrations continuously declined, with a half-life time of -104.5+/-28 minutes and -129.7+/-32 minutes, respectively. Serum decline of fPSA and tPSA followed a biphasic kinetic. During the initial alpha-phase, fPSA and tPSA serum concentrations decreased, with a half-life time of -69+/-10.3 minutes and -87.3+/-18.1 minutes, respectively. During the terminal beta-phase, the half-life time of fPSA and tPSA was -1152.2 minutes (0.8 days) and -3916.1 minutes (2.7 days), respectively. Between the alpha-phase half-life time of fPSA or tPSA and the half-life time of the total protein or albumin concentration decline, significant correlations were found. CONCLUSIONS These correlations indicate that the rapid decline of fPSA and tPSA directly after removal of the prostate (alpha-phase half-life time) is caused by the radical prostatectomy itself. The half-life time of the beta-phase reflects the biologic clearance of PSA. Therefore, the half-life time determination of PSA after radical prostatectomy is of limited value if the influence of the operation itself on the serum PSA concentration is not taken into account.