Prostatic acid phosphatase in 1993: Its limited clinical utility

The principal role of PAP determinations in 1993 with the ready availability of reproducible serum PSA determinations would be in the identification of those patients with clinically localized prostate cancer who will not be candidates for surgical cure because of the high likelihood of having pathologic stage C or D disease. However, if you believe that radical prostatectomy offers good local control and palliation for clinically localized but pathologic stage C or D disease, then preoperative PAP determinations are not necessary. Also, if you believe that radical prostatectomy in conjugation with androgen deprivation therapy is appropriate for clinically localized but pathologic stage D1 disease, then, again, preoperative PAP determinations are not necessary. However, if you believe that radical prostatectomy is indicated only for those patients with organ- confined cancer, then ordering a preoperative staging Roy enzymatic PAP assay is indicated. Therefore, every urologist must know the type of assay and the substrate being used by his/her laboratory to interpret the PAP results properly; otherwise, patients with potentially curable cancer will not be offered a radical prostatectomy. In conclusion, PSA is superior to PAP for diagnosis, screening, and monitoring prostate cancer. Even though there are three assays for PSA, there is less confusion in interpreting the results than for PAP. The only specific area where the enzymatic PAP assay can be useful is in the identification of those patients with clinically localized disease but pathologically extensive disease; this is not important if you believe that radical prostatectomy offers good local control and palliation for pathologic stage C and D1 disease. The result is helpful only if elevated (abnormal); if normal, it does not add any information. The more sensitive immunologic and radioimmune PAP assays are of no significant clinical value. In addition, the overall usefulness of the Roy enzymatic assay in the United States is obviously reduced by its limited availability. Difficulties in interpreting the results of the other enzymatic assays are potentially another serious problem in using PAP determinations. Thus, less than half of the urologists in the United States are even able to order the only PAP assay-the Roy enzymatic assay-that provides any unique or useful information over PSA values alone. Enzymatic PAP determinations should be performed only for preoperative evaluation of those patients with biopsy-proved localized disease; there is no need to do a 'screening' or 'monitoring' PAP, because PSA is the appropriate marker to follow and use for these purposes.