PSA AND ACID-PHOSPHATASE IN THE DIAGNOSIS OF PROSTATE-CANCER

Prostate specific antigen (PSA) and prostate acid phosphatase (PAP) ar e two well known markers for prostate cancer, PSA was isolated in 1979 and is biochemically a 33-kDa serine protease and in isomeric form. T he PSA blood test was developed in 1980 and has been most useful in th e: staging, monitoring, and early detection of recurrent: disease, PSA is of greatest value as a screening aid for the early detection of pr ostate cancer, Early-stage, organ-confined, nonpalpable, and clinicall y significant, but curable prostate tumors, have been detected by PSA and digital rectal examination. Several derivative PSA Bests, such as PSA velocity or slope, PSA density or index, age-specific referenced P SA ranges, and free versus complexed PSA have been examined to improve the diagnostic accuracy of PSA, Age-and race-specific PSA ranges and free PSA appear to enhance the ability of PSA to differentiate prostat e canter from benign prostatic hypertrophy, but large statistically va lid trials are still needed. The PSA immunohistochemical test was deve loped in 1981 to detect secondary metastasis: of prostate carcinoma. D etection of micrometastasis also has been improved. by reverse transcr iptase (RT)-polymerase chain reaction (PCR) of PSA-containing prostate cells in circulation, bone narrow, and lymph nodes. RT-PCR is still a n experimental tool at present, Prostate acid phosphatase (PAP) is the old ''gold standard'' for prostate cancer. Overall, PSA is a better d isease parameter than PAP. However, recent investigations on the basic biochemistry and molecular biology of PAP have provided new insight i nto its potential role in the diagnosis and therapeutic monitoring of prostate cancer.