Tumor markers in prostate cancer.

ABSTRACT

Prostatic specific antigen (PSA) is a tissue specific marker that is now the most widely used biochemical test for the assessment and follow-up of prostate cancer. The levels of PSA rise with tumor stage, but there is considerable overlap of their distribution between stages. PSA measurement now forms a part of the workup of a suspected carcinoma of the prostate, with a level of more than 4 ng/ml being an indication for further investigation. The sensitivity of PSA makes it an essential test for the postoperative assessment of radical prostatectomy and curative radiation therapy. The rates of change of PSA levels in locally advanced and metastatic disease treated by hormone manipulation can provide prognostic information. Low levels of PSA (less than 10 ng/ml) 6 months after treatment are a sign that the response will be prolonged. However, the sensitivity of PSA often results in a rising level preceding clinical evidence of progression by several months and is not necessarily an indication to change treatment. Alkaline phosphatase and prostatic acid phosphatase provide a less sensitive test for the bone response to skeletal metastases and tumor activity in advanced disease, respectively.