PERCENT FREE PROSTATE-SPECIFIC ANTIGEN VALUES IN MEN WITH RECURRENT PROSTATE-CANCER AFTER RADICAL PROSTATECTOMY

Objectives. Patients with prostate cancer may have more of the complex ed form of prostate-specific antigen (PSA) in the serum, whereas patie nts with benign prostatic hyperplasia have less of this complexed form and thus a higher proportion of the free form. However, the molecular basis for the lower percent of free PSA in patients with prostate can cer remains unknown, and considerable overlap in values exists. We exa mined this hypothesis in men with recurrent or persistent cancer after radical prostatectomy. These men, who have ''pure'' cancer in that th ey have no benign elements to their disease, should have very low perc ent free PSA values. Methods. Forty-six men with recurrent (persistent ) cancer as manifested by rising PSA values (mean [+/-SD] 2.4 +/- 2.5 ng/mL) after radical prostatectomy were available for analysis. Specim ens were analyzed with the use of the Abbott AxSYM free and total PSA assays. The Mann-Whitney U test was used to compare percent free PSA v alues in this recurrent cancer group with values from a previously def ined population of 415 men (225 with benign disease and 188 with prost ate cancer before prostatectomy). Results. Median values of percent fr ee PSA in the recurrent cancer group (8.4%) were significantly lower t han values in the preoperative cancer (11.7%) or benign (17.4%) groups (P <0.0001 for both comparisons). Among patients in the ''pure'' canc er group, 30 (65%) had values less than 10%; however, 4 patients (9%) had values from 15% to 19%, and another 4 (9%) had values of 20% or gr eater. Pathologically, patients with higher values (15% or greater) ha d aggressive disease. All patients with values of 20% or greater had e vidence of seminal vesicle involvement or nodal disease. Conclusions. Although most cancers exhibit low values of percent free PSA, a signif icant proportion of aggressive tumors will demonstrate high values. Un til this latter phenomenon can be explained, the widespread use of per cent free PSA to distinguish benign from malignant disease or to stage confirmed malignant disease should be approached with caution. UROLOG Y 52: 474-478, 1998. (C) 1998, Elsevier Science inc. All rights reserv ed.