Prostate-specific antigen in prostate cancer.

Prostate-specific antigen (PA) has been evaluated clinically as a tumor marker of prostate cancer with the use of enzyme immunoassay (EIA). For serodetection of prostate cancer, PA was assayed in a total of 1,109 sera. From mean +/- 3 S.D. of normal controls, upper cut-off values in males were decided as 2.5 and 1.2 ng/ml in Americans and Japanese, respectively. Serum PA values in prostate cancer patients were positive in 78% of Americans and 62% of Japanese. However, in benign prostatic hypertrophy (BPH) cases, a high false positive rate of 41% was observed in Americans. Simultaneous assays of serum PA and PAP showed high sensitivity and specificity in the detection of prostate cancer. This antigen could be used, as well as PAP, for monitoring prostate cancer patients. Furthermore, serum PA levels prior to treatment may express to some degree the malignant potential of the cancer. These results suggest that PA may be useful as a tumor marker of prostate cancer.