Immunoreactive prostatic acid phosphatase in prostatic cancer: diagnosis and followup of patients.

We compared the measurements of serum acid phosphatase activity to those obtained by radioimmunoassay of prostatic acid phosphatase in the sera of 126 untreated prostatic cancer patients. The catalytic activity of prostatic acid phosphatase was elevated in 32 per cent of the patients and the serum concentration of prostatic acid phosphatase was elevated in 66 per cent. Of these 126 patients 16 had stage T0-2M0N0-x disease, and enzyme activity and prostatic acid phosphatase concentration were increased in 0 and 38 per cent, respectively, in this group. Of the 110 patients with proved extracapsular cancer the corresponding figures were 36 and 70 per cent, respectively. We followed 109 of these 126 patients for 1 or more years after orchiectomy. A salient finding was that return of elevated serum prostatic acid phosphatase concentration to the health-associated reference interval within 7 days following castration indicated no progression of the disease at 1 year irrespective of the initial staging. The same was not detected by the measurement of catalytic activity of serum acid phosphatase. Our findings substantiate data showing that the measurement of circulating prostatic acid phosphatase is achieved better by immunological techniques than by measurements of catalytic activity of the enzyme. A novel aspect is the usefulness of immunological prostatic acid phosphatase measurements in evaluation of the prognosis of patients with metastatic prostatic carcinoma following ablative endocrine treatment.