PSA has become the most valuable tool for detecting, staging and monitoring prostate cancer in the past decade.31 After suggesting that the half-life of PSA might be a possible factor for the prognosis after radical prostatectomy, the pharmaco-kinetics of PSA gained more attention.32,33 PSA half-life is 2-3 days34 and a biphasic model for t/fPSA elimination was established.34 Lein etal. confirmed the biphasic elimination and suggested the first phase of free PSA loss might be the result of its rapid binding to a2-macroglobulin and ACT.35 Other investigators have assumed that the initial free PSA decrease was related to renal clearance or caused by the operation itself.36 In another study, the authors determined whether the assumed binding of PSA to its protease inhibitors after release into the circulation could be a possible reason for the elimination of free PSA. During the first 6 hours after radical retropubic prostatectomy, they found nearly constant levels of ACT-PSA and cPSA, in contrast to the rapid elimination of free PSA and a significant decrease in total PSA. From days 1 to
10, a continuous and nearly identical decrease of ACT-PSA and cPSA occurred compared to total PSA; free PSA was eliminated more rapidly. The first PSA decrease might be an effect of the operation itself or caused by renal elimination alone. The findings indicate that the initial rapid decrease of free PSA immediately after surgery could be caused by new complex forming of PSA with ACT and other serum protease inhibitors.37
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