MONITORING PERCENT FREE PSA IN SERIAL SPECIMENS - IMPROVEMENT OF TESTSPECIFICITY, EARLY DETECTION, AND IDENTIFICATION OF OCCULT TUMORS

We have measured the serum concentration of prostate specific antigen (tPSA) and determined the percent free PSA (% fPSA) in serial specimen s from 64 patients with prostate cancer, 35 patients with benign prost ate hyperplasia (BPH), and 3 patients with prostitis. We found that th e % fPSAs were not a constant for individual patients during the cours e of the disease. When we compared only the % fPSA of the first specim en of serial specimens from individual patients, who were largely untr eated, 37% of BPH specimens were above 22%, whereas only 1.6% cancer s amples were above that value. We also found that 67% of cancer specime ns and 14% of BPH samples were below 8%, respectively. Although % fPSA distribution pattern remained similar between two types of specimens, less differentiation was found between BPH and prostate cancer in ran dom specimens compared to the study using first specimens of an indivi dual patient's serial samples. Percent fPSA apparently are affected by treatment. However, the most important benefit for the determination of % fPSA appears to be the sensitivity of % fPSA to identify occult t umors when the tPSAs were in the normal concentration range. Determina tion of % fPSA also seems to improve the specificity of tPSA, not only during screening for the differentiation between BPH and prostate can cer, but also during monitoring of treatment and recurrence. (C) 1998 Wiley-Liss, Inc.