Is the determination of prostatic acid phosphatase still worthwhile in prostate cancer patients?

With the introduction of prostatic specific antigen (PSA), the role of prostatic acid phosphatase (PAP) has been questioned. Some authors still advocate its determination, because PAP may be helpful for identifying patients with organ confined cancer. Tumor progression may be detected earlier in some patients by PAP. With respect to cost, we analyzed whether PAP still has a place as a tumor marker for prostate cancer (PC). In 6,151 men seen for screening or treatment of PC or therapy of benign prostatic hyperplasia (BPH), parallel determinations of PAP and PSA were done. PC was diagnosed in 862 patients, BPH in 5,503 patients, and prostatitis in 86 patients. There were only 16 patients with PSA < 4 ng/ml and PAP > 5 ng/ml. Five of 16 patients had histologically proven BPH; 11 of 16 patients suffered from metastatic PC. Five of 11 patients were in remission on hormonal therapy; PSA had already normalized and PAP was still elevated. Three of I I patients had hormone resistant PC; PAP detected the progression earlier than PSA. In the absence of an effective treatment, this is not of clinical relevance. In 1 of 11 patients, a falsely low value was assumed. In all, 935 of 6,151 patients showed normal PAP and elevated PSA; 805 of 935 patients suffered from BPH or prostatitis; 130 of the 935 patients had PC. Stage D was found in 56 of 130 patients, stage C in 31 patients, and stage A B in 43 patients, which did not allow the identification of organ confined cancer. Therefore, there is no benefit from the determination of PAP in PC. It is both safe and cost-effective to abandon PAP as a tumor marker for PC.