The Impact of Intraoperative Manipulation of the Prostate on Total and Free Prostate-Specific Antigen

Abstract

Objectives It is well documented that mechanical manipulation of the prostate can elevate total PSA (t-PSA) levels in serum. However, less is known about its effects on free PSA (f-PSA) and the free-to-total PSA ratio (f/t-PSA). We therefore examined the impact of prostate manipulation on t-PSA and f-PSA during surgical procedures involving the prostate. Methods Intraoperative blood samples for t-PSA and f-PSA measurement (Hybritech) were collected every 15 min during 14 radical retropubic prostatectomies (RRP) and 10 radical cystoprostatectomies (RCP). Results Prostatic manipulation induced significant elevations in t-PSA and f-PSA during RRP and RCP. Postmanipulatory peaks were markedly higher for f-PSA than for t-PSA. The mean maximum f-PSA levels showed a 4.3- (RRP) and 7.9-fold (RCP) increase, followed by a rapid decline after prostate removal. t-PSA increased 1.2- (RRP) and 1.3-fold (RCP), and declined more slowly. Postmanipulatory f/t-PSA ratios also increased significantly, reaching mean elevations of +0.29 and +0.28 over preoperative ratios during RRP and RCP, respectively. Conclusions Prostate manipulation can induce transient increases in t-PSA, f-PSA and f/t-PSA in benign and malignant prostates. The extent of these alterations and their course over time must be taken into account when postmanipulatory changes in PSA forms are investigated. Timing of postmanipulatory venipunctures and the molar response ratio of t-PSA assays used (equimolar versus nonequimolar) seem to have substantial impact on the results of such studies.