PROSTATE-SPECIFIC ANTIGEN AS A UNIQUE ROUTINE TEST IN MONITORING THERAPY FOR INOPERABLE PROSTATE-CANCER - COMPARISON WITH RADIONUCLIDE BONE-SCAN AND PROSTATIC ACID-PHOSPHATASE

The aim of the present investigation was the evaluation of cost-effect iveness of variables used in monitoring patients with inoperable prost ate cancer. Prostate-specific antigen (PSA), prostatic acid phosphatas e (PAP), and radionuclide bone scan were considered. The tumor marker positivity was assessed according to dynamic criteria (>50% increase b etween consecutive samples). 108 patients entered the study; 72 patien ts treated with a luteinizing hormone-releasing hormone analogue were followed up for periods ranging from 12 to 64 months. PSA and PAP leve ls were measured using immunometric assays. Both cutoff-based and dyna mic, serial sample-based deicision criteria were employed. With respec t to a positive bone scan, PSA showed negative predictive values of 82 and 77%, respectively, using 4 and 10 ng/ml as cutoff points. Progres sion of the disease to the bone occurred in 20 patients: in 17 PSA was the first indicator of progression, in the other 3 PAP anticipated PS A for a very short time (3-4 months), which was not of relevance to cl inical decisions. PAP is less specific and sensitive than PSA; PAP may eventually provide information on disease status in a limited percent age of patients with advanced prostate cancer treated with androgen ab lation, being differently regulated with respect to PSA. No increasing PSA profile was detected in patients who responded to the therapy. Fr om the results of the present investigation, we draw the following con clusions: (1) PSA can be used reliably as a unique tool in the follow- up of patients for the early detection of progressive disease, and (2) dynamic criteria of evaluation of serial PSA determinations probably provide more effective and earlier clinical information.