Prospective comparison between serum monoclonal prostate specific antigen and acid phosphatase measurements in metastatic prostatic cancer.

Prostate specific antigen, prostatic acid phosphatase antigen and acid phosphatase activity were measured on 175 serum samples serially collected from 80 patients with metastatic stage D adenocarcinoma of the prostate. Prostate specific antigen and prostatic acid phosphatase antigen concentrations were measured with a monoclonal radioimmunometric assay, and acid phosphatase activity was measured enzymatically. The over-all frequency of abnormal levels of prostate specific antigen (76 per cent) was significantly greater than abnormal prostatic acid phosphatase antigen (60 per cent) and acid phosphatase activity (49 per cent) results (p less than 0.001). These differences were greater among the subset of patients in clinical remission. Levels greater than 10 times normal were observed in 68 per cent of prostate specific antigen, 43 per cent of prostatic acid phosphatase antigen and 31 per cent of acid phosphatase activity measurements (p less than 0.001). Three or more serial prostate specific antigen measurements in 17 patients demonstrated excellent correlation with independently assessed clinical disease activity. These results suggest that prostate specific antigen is a more sensitive and potentially more useful tumor marker than acid phosphatase measurements in patients with metastatic prostatic carcinoma.