Serum and bone marrow radioimmunoassay of acid phosphatase in prostatic cancer

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.

Lack of value of radioimmunoassay for prostatic acid phosphatase as a screening test for prostatic cancer in patients with obstructive prostatic hyperplasia

We examined the incidence of prostatic cancer in patients with an elevated radioimmunoassay for prostatic acid phosphatase and clinical benign prostatic hyperplasia on digital rectal examination. Of 295 patients screened with prostatic acid phosphatase tests 17 fulfilled the criteria of having an elevated prostatic acid phosphatase, clinically benign prostate and histological examination of the prostatectomy specimen. None of the 17 patients had histological evidence of prostatic cancer. The results confirm the predictions of mathematical models that prostatic acid phosphatase is of no practical value as a screening test for prostatic cancer in patients with clinical benign prostatic hyperplasia.

The effect of rectal examination on serum acid phosphatase levels in benign and malignant prostatic disease

Serum acid phosphatase was measured in patients with enlarged benign and malignant prostate before and after rectal examination. Amongst the patients with benign glands, rectal examination did not produce any significant false elevation of the enzyme. Rectal examination, however, caused a rise in the enzyme level in a few untreated cancer patients and in cancer patients who had become refractory to hormonal therapy. This rise would help rather than mislead in the diagnosis of malignant prostate and also in identifying treated patients who had become refractory to treatment. Thus, when serum acid phosphatase is properly determined, elevated levels should always arouse suspicion of malignant prostate or other lesions associated with high enzyme level even if such determination was preceded by rectal examination.

There appears to be no merit in the teaching that the determination of serum acid phosphatase should be delayed after rectal examination.