EVALUATION AND COMPARISON OF 2 NEW PROSTATE CARCINOMA MARKERS - FREE-PROSTATE SPECIFIC ANTIGEN AND PROSTATE-SPECIFIC MEMBRANE ANTIGEN

BACKGROUND. Two new prostate cancer markers; free-prostate specific an tigen (f-PSA) and prostate specific membrane antigen (PSMA) were recen tly introduced. This report summarizes a prospective two-year multicen ter test of their diagnostic or prognostic capabilities. Total PSA was also measured. METHODS. There were four clinical groups studied: (1) 226 individuals from a screening project undergoing ultrasound and bio psy evaluation had markers obtained: (2) 68 patients suspected of havi ng prostate cancer and undergoing 2 or more biopsies had the markers o btained on multiple occasions: (3) 100 patients undergoing radical pro statectomy had markers obtained pre- and post-operatively: and (4) 31 patients with metastatic prostate cancer each had multiple samples for marker assay obtained over a 2-year period. In all, 465 patients had one or more samples obtained and studied. RESULTS. Free-PSA affords li ttle additional diagnostic advantage compared with total PSA in the sc reening population. The reciever operating characteristic curves for d iagnostic accuracy were ranked: (1) PSA density; (2) total PSA; (3) f- PSA; and (4) PSMA. PSMA showed the best correlation with stage of the primary tumor in the screened group. In the multiple negative biopsy g roup, f-PSA varied from 12 to 21%. PSMA values were evaluated in all h istologic categories. PSA density was greater than or equal to 0.15 in all categories. In the prostatectomy cases PSA values postoperatively were quite low in Stage II; f-PSA was of no value. Later, f-PSA was i ncreased In association with elevated total PSA values. Mean PSMA valu es were above normal in all postoperative time periods except in Stage III patients at 6 months to 1 year postoperatively. PSA densities wer e all greater than or equal to 0.15. In patients with metastatic carci noma, elevated PSMA values correlated best with a poor prognosis (clin ical progression), as has been described. CONCLUSIONS. These data sugg est that f-PSA values do not provide additional diagnostic benefit com pared with total PSA in screening populations, in the presence of susp ected cancer, postprostatectomy, or in metastatic disease. PSMA is of prognostic significance, especially in the presence of metastatic dise ase, and correlates well with the stage of disease in cancers detected in a screened population. (C) 1996 American Cancer Society.