An evaluation of the immunochemical measurement of prostatic acid phosphatase and prostatic specific antigen in carcinoma of the prostate.

Serum prostatic specific antigen (PSA) and prostatic acid phosphatase (PAP) were evaluated with double monoclonal radioimmunoassays. In 250 patients with prostatic cancer the normal limits were as follows: PSA 0.1-2.7 ng/ml, and PAP 1.09 +/- 0.45 ng/ml (mean +/- SD). In 91 untreated patients with non-metastatic tumours, 42.8% had PSA greater than 10 ng/ml and 18.6% had PAP greater than 2 ng/ml. In 60 untreated patients with metastatic disease PSA was greater than 10 ng/ml in 91.7%; PAP was greater than 2 ng/ml in 65%. In prolonged remission PSA was generally less than 5 ng/ml and PAP less than 2 ng/ml. Longitudinal studies of 2-4 years showed the independence of these markers and a higher correlation of changes in the PSA level and clinical status than given by parallel PAP measurements. In non-metastatic disease, PSA greater than 10 ng/ml at presentation, with or without a coincidentally raised PAP, carried an increased risk of progression within 2 years.