SERUM PERCENT FREE PROSTATE-SPECIFIC ANTIGEN IN METASTATIC PROSTATE-CANCER

Objectives. To define the serum prostate-specific antigen (PSA) isofor m profile in patients who have prostate cancer but do not have a prost ate gland, that is, men who have had a previous radical prostatectomy (RP) and subsequently persistent disease as evidenced by elevated PSA. PSA can be reliably measured in the serum in two major isoforms: PSA complexed to alpha(1)-antichymotrypsin and uncomplexed free PSA (fPSA) . Multiple investigations have illustrated the usefulness of the free/ total PSA proportion (percent fPSA) in differentiating prostate cancer from benign prostate disease in patients who still have their prostat e gland in situ. Methods. Sera were evaluated from 52 men who underwen t RP and postoperatively had increased PSA. fPSA and total PSA (tPSA) concentrations were determined using the Abbott AxSYM PSA assays. Perc ent fPSA was calculated for all patients.Results. Median tPSA was 5.45 ng/mL (range 0.93 to 214.99). Median fPSA was 0.69 ng/mL (range 0.11 to 54.93); the median percent fPSA was 13.3% (range 3.9% to 62.9%). Th ere were 27 (52%) patients with percent fPSA less than 15%, 25 (48%) p atients with greater than 15%, and 7 (13%) with greater than 30%. No s ignificant relationship was found between percent fPSA and grade, stag e, and severity of disease. Percent fPSA was significantly increased i n patients who received hormonal, radiation, or combination treatment versus those who received no treatment (P = 0.02 to 0.0007). Conclusio ns. Serum percent fPSA in men after RP with persistent prostate cancer encompasses a wide range of values with no clear stratifying factor o r factors. These observations and further serial studies in patients w ith progressive metastatic disease may be important in determining the mechanism(s) for lower percent fPSA in men with newly diagnosed prost ate cancer. UROLOGY 52: 366-371, 1998. (C) 1998, Elsevier Science Inc. All rights reserved.