A new method for estimating serum acid phosphatase of prostatic origin applied to the clinical investigation of cancer of the prostate.

Since the studies of Gutman and Gutman (2, 3), measurements of the serum acid phosphatase have become a recognized and widely used ancillary procedure for the diagnosis of cancer of the prostate and a practical means for the evaluation of the functional status of the tumor in many patients with metastasizing cancer of the prostate. While an abnormally increased value of serum acid phosphatase is considered to be a specific index for the presence of carcinoma of the prostate, a normal serum acid phosphatase value in itself cannot be interpreted as signifying absence of this disease. According to Bodansky and Bodansky (4) in their review of the literature, only 24 per cent of unselected patients without and 81 per cent with bone metastases from cancer of the prostate show elevated serum acid phosphatase values. Thus, 20 to 75 per cent of proven cases of cancer of the prostate show equivocal or normal serum acid phosphatase levels. Attempts have been made to render the determination of serum acid phosphatase more specific for cancer of the prostate. Thus, a search has been made for substrates which would be split prefer-